Licensure Examination in Agriculture Reviewer: Soil Science

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Soil Science

Jofil Alao Mati-om Green Empire P.H is an online support group providing basic knowledge in agriculture especially to those who are planning to take the Licensure Examination in Agriculture in the Philippines.

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Support Team Basic Information:

Marcial S. Buladaco

Jofil Alao Mati-om

Audio by Paper2Audio.

Maluz A. Belarma

Michelle Ann M. Calubaquib

Lovely R. Luar

Ma. Theresa V. Velasco

2. O.M content

Organic colloids

Inorganic colloids

1. Crystalline silicate clays 2. Amorphous (non-crystalline) silicate clays

Actinomycetes

Algae

Soil Organic Matter (S.O.M)

Effects of organic matter to soil properties

1. Physical

2. Chemical

3. Biological

S.O.M decomposition

Carbon/Nitrogen ratio

◆ Microbial transformations of N

1. Mineralization

2. Immobilization

3. Nitrification

4. Denitrification

5. Ammonification

6. Symbiotic biological N fixation

7. Non symbiotic N fixation

Inorganic P solubilization

◆ Microbial transformation of sulfur

Iron precipitation by soil bacteria

Composts and composting

♦ Cellulose decomposition

6. Principles and Management of Soil Fertility

Soil fertility

Soil productivity

♦ Plant nutrition

✓ Nutrients

Metabolic processes

The 17 essential elements

Criteria of essentiality

Macronutrients

Micronutrients

Mobile nutrients

Immobile nutrients

Mechanism of nutrient movement

1. Mass flow 2. Diffusion

3. Contact exchange

Carrier theory of nutrient uptake

♦ Difference between passive and active uptake

Nitrogen uptake

♦ Phosphorus uptake

Potassium uptake

Calcium uptake

Magnesium uptake

Sulfur uptake

Yield response to increasing nutrient supply

♦ Liebig's Law of Minimum

♦ Mitscherlich's equation

♦ Growth factors

1. Temperature

2. Moisture supply

3. Solar energy

4. Soil properties

Soil fertility evaluation

1. Quantitative methods

2. Qualitative methods

Soil analysis

Soil sampling

♦ Plant analysis

Fertilizer field trials

Pot experiment

Nutrient deficiency symptoms

Fertilizer

♦ Rationale for fertilization

Organic fertilizers

Inorganic fertilizers

Conventional units of expressing fertilizer nutrients

Common N fertilizers

Common K fertilizers

C factor

P factor

♦ 9 Suitability classes of soil

Soil Science

1. {Concept of Soil}

♦ {Soil}

- a mixture of organic and inorganic materials which developed on the earth's surface through weathering process of rocks and minerals and whose properties are conditioned in various degrees by the influence of climate, living organisms, and topography acting on the parent material over a period of time

- serves as a medium of plant growth (physical support for anchorage of plant roots; water and nutrient supplier)

- ∞ considered a non-renewable resource because it takes about a hundred years for natural processes to form an inch of soil

- ∞ a natural body with dimensions of thickness and width with indistinct horizontal boundaries enabling it to blend with other soils and vertical boundaries of the air above it and the unweathered rocks below it

♦ Soil surface

∞ this term is based on the upper limit of soil which is the boundary between soil and either air, shallow water, live plants, or plant materials that have not begun to decompose

♦ Soil individual

1. Pedon

- a hexagonal column of soil measuring from 1 to 10 m in top surface area

- infinity the basic sampling unit used in soil surveys

2. Polypedon

- an essential soil individual, comprising an identifiable series of soils in an area

- made up of multiple pedons and has distinctive characteristics that differentiate it from surrounding polypedons

♦ Approaches in the study of soil

1. Pedological approach

- (Greek: pedon, soil or earth) the study of soils with principal interest on characterization and differentiation of their properties and with only minor emphasis on their practical use

- Ex. Study of soils for their taxonomic classification; soil as a natural body

2. Edaphological approach

- (Greek: edaphos, soil or ground) the study of soils with emphasis on their practical use, particularly the relationship of soil properties to plant growth

- ∞ Ex. Study of soil fertility; Variability of soil productivity; Methods of conserving and improving productivity

Fields of study in Soil Science

1. Soil Fertility: quality of a soil to provide optimum level of nutrients for plant growth

2. Soil Physics: characteristics, processes, or reactions of a soil caused by physical forces

3. Soil Chemistry interactions of solid, liquid, and gaseous phases or components of soil

4. Soil Microbiology: soil biochemical reaction carried out primarily by microorganisms

5. Soil Conservation and Management: protection of soil against physical loss by erosion or chemical deterioration; totality of all tillage operations, cropping practices, fertilization, liming etcetera conducted on a soil for crop production

6. Soil Survey and Classification: deals with the structural characteristics, mode of origin, and systematic arrangement of soils

7. Soil mineralogy : structural chemistry of the solid components of soil

8. Land use: deals with the allocation of lands for general or broad purposes such as agriculture, forestry, settlement and military reservations

♦ Different components of soil-the proportion of the different components varies in properties among soils

1. Soil solids

- infinity Mineral matter, 45 percent

- comes from the weathering of rocks and minerals

- composed of sand, silt, and clay particles vary among soils

- major source of all nutrient elements (except nitrogen, carbon, and oxygen) needed for plant growth

∞ Organic matter, 5%

derived from the decayed and decaying remains of plants and animals intimately mixed with the mineral matter

the chief natural source of nitrogen; indicative of the nitrogen status of the soil

○ also contributes phosphorus, sulfur, and micronutrients but in smaller amounts compared to mineral sources

enables the soil to store cations

promotes the formation and stabilization of aggregates, giving the soil greater permeability and porosity

Organic soils contain more than 20% organic matter; most soils contain less than 20% organic matter, thus classified as mineral soils

2. Pore spaces

infinity Air, 20 to 30 percent occupies the pore spaces of the soil

composed largely of elemental nitrogen (78%), oxygen (20%), carbon dioxide (0.5%), and traces of other gases

○ provides oxygen for respiration of plant roots

For dryland or upland crops, it is ideal that at least half of the pore spaces be occupied by air.

There must be enough aeration at the root zone for easy exchange of carbon dioxide and oxygen between the soil pores and the aboveground atmosphere so that carbon dioxide would not build up to high levels which can be toxic to plant roots.

The C-O 2 in soil air is typically higher in concentration than that above-ground because of the accumulation from C-O 2 evolution from organic matter decomposition, plant root respiration, and reaction products of carbonate materials.

∞ Water 20 to 30%

○ also occupies the pore spaces of the soil

contains dissolved gases and salts or compounds as well as dissociated ions of various nutrient elements

carries the nutrients to the proximity of roots where they can be absorbed

also serves as a weathering agent of minerals to constantly renew the nutrient supply in the soil

○ needed by the plant in large amounts for their metabolic functions

○ In paddy soils such as in lowland rice fields, the pore spaces are nearly filled with water.

The dissolved C-O 2 in soil water forms carbonic acid which is a solvent that can release nutrients from minerals.

2. {Weathering and Soil Formation}

♦ Rocks : aggregates of minerals

Petrology: study of rocks

3 General classification of rocks

1. Igneous rocks

- ∞ original rocks formed from the solidification of molten magma at temperatures of 900 degrees Celsius to 1600 degrees Celsius within or outside the earth's crust

- The most common soil-forming igneous rocks are granite, diorite, gabbro, ryolite, andesite, basalt, and obsidian

- ∞ Granite and diorite are lighter in color due to the high proportion of light-colored minerals such as feldspar and muscovite.

- ∞ Gabbro is dark in color due to the predominance of dark-colored minerals such as biotite, hornblende, and augite.

- Granite is acidic while basalt is basic.

- Basalt and andesite are among the dominant soil-forming rocks in the Philippines. Examples are the soil series of Adtuyon, Antipolo, Guimbalaon, and Jasaan

2. Sedimentary rocks

- formed from other existing rocks through fragmentation, transport (by water) and recementation

- concentrated near the crust's surface, thus exert a dominant effect on many soils of the world

- The most important soil-forming sedimentary rocks are limestone, dolomite, sandstone, and shale.

- Limestone is made up chiefly of the carbonate mineral, calcite or calcium carbonate.

- Dolomite is also a carbonated material composed of calcium magnesium carbonate C A M g open parenthesis C O 3 close parenthesis squared.

- Infinity Sandstone is composed of cemented sand grains.

- ∞ Shale is made up of fine particles of clay which become consolidated after deposition in bodies of water.

- Soils derived from shale/ sandstone are soil series of Alaminos, Bantay, Bauang, Lugo and Ubay.

- Soils derived from limestone are soil series of Faraon, Bolinao, Binangonan, and Alimodian which are the soils in Cebu and Bohol.

3. Metamorphic rocks

- formed from other existing rocks through the processes or remelting and recrystallization under very high temperature and pressure

- The most typical soil-forming metamorphic rocks are gneiss, schist, quartzite, slate, and marble.

- Marble is the metamorphic form of limestone.

2 Modes of rock formation

1. Extrusive (volcanic) formation

- ∞ happens when the magma is ejected out of the earth's crust through volcanic eruption and solidifies on the surface

- There is abrupt cooling of the magma and less time for crystal growth.

- The rock formed is fine-grained. Ex. basalt

2. Intrusive (plutonic) formation

- infinity happens when magma solidifies within the earth's crust

- ∞ There is more time for crystal growth of the magma because of slow cooling due to high temperature.

- The rock formed is coarse-grained. Ex. Granite

8 Most abundant elements in the earth's crust

1. Oxygen (46.6%)

2. Silicon (27.7%)

3. Aluminum (8.13%)

4. Iron (5.0%)

5. Magnesium (2.09%)

6. Calcium (3.63%)

7. Sodium (2.83%)

8. Potassium (8.13%)

Mineral

a naturally occurring inorganic substance with more or less definite chemical composition and specific physical properties

infinity serves as building block of rocks

Mineralogy : study of minerals and their properties

2 General classifications of minerals

1. Primary minerals

Infinity persist in the soil in their original state due to high resistance to decomposition

infinity chief sources of the sand and silt fractions of soils

infinity Some of the most important primary minerals

• Quartz, SiO _{2} (microline): a predominantly Quartz parent material is expected to give rise to sandy soils; does not contribute to soil fertility because of its main composition of SiO _{2}

O Orthoclase, K Al Si 3 O 8 (anorthite) : contributes K upon weathering

Sodium-plagioclase, Na Al Si 3 O 8 (albite) : contributes Na upon weathering

Calcium-plagioclase, Calcium Aluminum 2 Silicon 2 Oxygen 8 : contributes Calcium upon weathering

○ Muscovite, K Al 3 Si 3 O 10 (O.H) 2 (white mica)

○ Biotite (black mica)

○ Hornblende

o Augite

○ Apatite

2. Secondary minerals

- infinity arise from the chemical breakdown of the least resistant primary minerals

- infinity contributes the clay fraction to the soil

The more commonly occurring secondary minerals are:

- Calcite

- Dolomite

Gypsum

o Limonite

○ Hematite

Gibbsite

○ Kaolinite

Montmorillonite

○ Illite

2 Types of weathering of rocks and minerals

1. Physical weathering

- ∞ breaking up or rocks and minerals into smaller pieces without any drastic alteration of their chemical composition

Example: Unloading which refers to the imperceptible movement of rock formation towards the earth's surface resulting in cracking or rocks.

Example: A freezing water in narrow cracks in the rocks can cause physical disintegration due to expansion and contraction in response to the alternate cooling and heating.

2. Chemical weathering

- ∞ involves change in the chemical structure and composition of rocks and minerals which results into simpler products

- infinity The processes involved are

- Hydrolysis : the reaction of water with the mineral resulting in the destruction of the original chemical structure and the formation of an acid and base

Ex. Potassium feldspar reacted with water to form silicic acid and potassium hydroxide (base)

- Hydration: also involves the reaction of water with the mineral but not leading to the destruction of the chemical structure; The result is a rigid attachment or association with a water molecule.

Ex. The transformation of hematite to limonite

- Oxidation: changes the iron in the mineral from ferrous (reduced) to ferric (oxidized) form; the reduction in size and increase in valency of Fe results in the weakening and instability of the mineral's structure

Ex. Ferrous oxide to hematite

○ Carbonation: the reaction of carbonic acid (H 2 C-O 3) with a mineral to produce a more soluble product

Ex. The transformation of calcite to calcium bicarbonate

- Solution: the dissolution of minerals through the solvent action of H 2 C-O 3 or H plus ions which results into the separation or dissociation of component cations

Ex. Silica is dissolved from minerals and washed off from the soils.

Stages of soil formation: Rocks and its component minerals undergo weathering resulting into the partially broken parent material. Further weathering allows development of soil horizons.

1. Physical weathering: reducing the size of the parent material (rocks and minerals) particles

2. Rearranging the mineral particles 3. Adding of organic matter

4. Chemical weathering: changing the composition and structure of minerals including clay formation

5. Formation of soil horizons

5 Factors of Soil Formation (Clorpt)

1. Climate affects the amount of leaching that takes place in the soil and the speed with which soil horizons develop

∞ Temperature

- As the mean annual temperature increases, the weathering of rocks and minerals in the soil will be faster.

- For every 10 degrees Celsius rise in temperature, the rate of biochemical reactions doubles.

- Tropical soils will weather faster because of faster chemical reactions which can occur throughout the year.

∞ Rainfall

Areas with more rainfall will have greater weathering (hydration and hydrolysis) and greater leaching.

Leaching occurs when water moves through the soil and removes the soluble constituents.

Soluble silica and bases are leached out to give rise to soils high in kaolinite and sesquioxides.

Water is an agent of erosion and deposition of soil materials.

At optimum levels, water facilitates decomposition of organic matter.

Cool and wet areas will have more leaching than hot and wet areas.

○ In areas with low rainfall, silica and basic cations like Ca, Mg, Na and K accumulate and form monmorillonitic soils.

Hot and dry areas have slower soil formation resulting to a shallow solum.

2. Living organism

- affects soil formation through their effect on the amount and kind of organic material decomposed and accumulated

- Vegetation affects the thickness and color of the surface horizons.

- infinity Bioturbation: the mixing of the soil by organisms

- Soils of forested areas (dipterocarps) have thin surface horizon, leached, light colored zone below the surface and an accumulation zone that is often brown or red in color.

- Soils of grassland areas have thick, black surface horizon.

3. Relief or Topography

- The shape or contour of the land surface affects the movement and accumulation of water which can modify the effect of the climate factor.

- ∞ Steep slopes: less water to soak the soil but more runoff to erode the surface thus preventing the formation of a thicker soil profile

- Flat lowlands: develop thicker solum due to accumulation of moisture and deposition of soil materials from the uplands

- Soils at the summit and shoulder will develop horizons the fastest.

- Soils on the backslope will develop slower.

- Soils at the footslope will collect sediments from the upslope.

4. Parent material

- infinity the partly weathered mineral or organic debris from which true soil (solum) is formed

- the starting point of soil formation at zero time of formation

- infinity 2 general classification of parent material

- sedentary or residual those that develop in place and formed from the rock below where it is found

- transported those which are transported by various agents and deposited in other sites where they form the soil. The different types based on the agent and manner of transport are the following:

- Alluvium: accumulated from running water that is rivers and streams; Ex. Soils surrounding the Cagayan river; the central plains of Luzon

- Lacustrine materials that are accumulated in former lakewaters

- Marine: materials that are accumulated in former oceans

- Glacial till or moraine: those that are carried and deposited by moving glaciers

- Aeolian : those that are carried and deposited by the wind; Ex. Sand

5. Time

dunes; extensive soils around Taal volcano developed from volcanic ash

- Volcanic tuff: a stratified rock hardened (lithified) from deposited fine dust or ash emitted on a volcanic eruption; Soil series of Lipa, Guadalupe, Ibaan, Magallanes, Tagaytay, Novaliches, and Taal are formed from volcanic tuff parent material.

- Collovium : those transported and deposited by gravity

- ∞ (age of soil) the length of time in years since the land surface became stable; depends on how much development the soil has undergone

- infinity A young soil has minimal soil development and few horizons.

- ∞ Alluvial soil is generally a young soil because of the constant deposition which renews the parent material.

- The older the soil, the less it reflects the properties of the parent material.

- As development proceeds, more of the soluble components particularly the bases are leached out.

- Old soils have thick solum but are generally acidic and low in fertility.

- Soil profile : a vertical cross section of the soil exposing all of its horizons

- Soil horizon : a layer of soil or soil material approximately parallel to the land surface and differing GreenEmpire P.H (facebook dot com U.R.L) from adjacent horizons in physical, chemical and biological properties

- Horizon differentiation: process wherein each horizon acquires distinctly different properties from the others due to various mechanisms of addition, losses, translocation and transformation

Mechanisms of Addition and Transformation

1. Enrichment : general term for the addition of any material to the soil body

2. Melanization : admixing of organic matter to the mineral matter which darkens the soil

3. Cumulization: addition of mineral matter trough wind and water to the soil body

Mechanisms of translocation

1. Illuviation : general term for the movement of soil material from one part of the soil to another resulting in the formation of argillic (clayey) layers

2. Calcification: the transfer and accumulation of calcium carbonate in particular soil horizon

3. Decalcification: removal of calcium carbonate from the soil horizon

4. Salinization: accumulation of soluble salts of sulfates and chlorides of calcium, magnesium, sodium and potassium in certain horizons; Opposite: Desalinization v. Alkalinization (solonization): accumulation of sodium ions; Opposite: Dealkalnization (solodization)

6. Podzolization (Silication) : the translocation of aluminium and iron and/or organic matter thus, concentrating the silica in the leached layer

7. Laterization (Desilication): the transfer of silica from the solum, thus concentrating the aluminium and iron oxides and sesquioxides in the leached layer

8. Leucinization : paling or loss of dark color of the soil due to the removal of organic matter from the solum

9. Lessivage : specific term for the movement of fine mineral particles from the top soil resulting in the enrichment of clay on the lower horizon

♦ {Solum} : A and B, zone of pedogenic activity; considered as the true soil because these are the layers reached and used by the roots as source of water and nutrient

• Pedoturbation : the biological (by soil organisms) and physical (freezing, thawing, wetting, drying) mixing of soil materials resulting into the homogenization of the solum

♦ Regolith : all loose materials above the bedrock (A,B, and C horizons)

1. One capital letter is used to designate master horizons (A,B,C)

2. Two are used for transitional horizons (A.B,BC)

3. Lowercase subscripts are used to subdivide master and transitional horizons (Bt,Ap) and to designate important horizon properties

4. Descriptive soil profile symbols O: Horizon dominated by organic matter

- A: Organic-rich, mineral horizon at or adjacent to the surface E: Mineral horizon of maximum eluviation B: Mineral horizon of maximum illuviation and formed beneath an O,A, or E C: Weathered parent material R: underlying consolidated bedrock

- Surface Horizons: mainly influenced by the addition of organic matter O: surface litter – Oi, Oe, Oa A: topsoil - Ap A.B: transition horizon Subsurface horizons: developed due to the translocation, transformation and losses E (zone of leaching) – B (subsoil) – Bt, Bw, Bk C. horizon: weathered parent material; outside the zone of soil development; little altered by soil forming processes R horizon: bedrock; impenetrable layer

3. {Physical Properties of the Soil}

Soil Texture

- infinity the relative proportion of the various size fractions: sand, silt and clay in the soil infinity a relatively stable property of the soil

No amount of organic matter added can alter soil texture since it is determined by proportions of the inorganic components sand, silt and clay.

When flooding deposits huge amounts of any of these fractions in an area, then that is the case when soil texture can change/

Soil texture can also change when volcanic eruption deposits huge amount of sand-sized particles in an area.

- ∞ Generally, coarse-textured soils are less fertile because they contain many primary minerals such as plagioclase feldspars, quartz, and magnetite with low bases and do not release many nutrients important to plants. They are also easily leached.

- ∞ Upland crops are more suitably grown in coarse to medium-textured soils, particularly the tuber crops where the tubers can more easily develop.

Fine to medium-textured soils are more suitable for growing paddy rice because water can be impounded longer than in sandy soils.

Soil separates and their characteristics

- Infinity Sand particles are the largest fractions and are more or less rounded.

- Particles of sandy soils are more loosely cemented so they are easier tilled even when wet or dry.

- infinity Relationship between particle size and surface area:

- The smaller the particle size, the greater is the total surface area of a given mass of soil.

- Clayey soils have greater surface area than sandy soils.

The sand and silt fractions provide for the framework for the soil because of their bigger particle sizes

Large spaces in between sand and silt particles facilitate air and water movement, so coarse-textured soils are better drained.

Clayey soils are generally more fertile but tend to be plastic and sticky when wet.

Clayey soils have greater water holding capacity because of greater total volume of pore spaces.

- ∞ Water moves slowly in clayey soils but farther in the long run because the water channels are mostly through capillary pores.

References for soil separates diameter: (U.S.D.A) United States Department of Agriculture and (Issa) International Soil Science Society Textural Triangle: shows the percentage of sand, silt and clay at various textural classes. To find the textural class of soil in the Textural Triangle given their respective percentages f soil separates, simply find the intersection point where the soil separates meet.

Lifted from http://www.public.iastate.edu/~arossi/texture%20triangle.jpg

Table 1 summary: Soil separates are categorized by their particle diameter, physical feel, mineral composition, and shape. Sand particles range from 2 to 0.05 millimeters under USDA standards or 2 to 0.02 under ISSA standards, feeling coarse and gritty with a cubic to spherical shape derived from primary minerals like quartz and feldspars. Silt particles range from 0.05 to 0.002 millimeters by USDA or 0.02 to 0.002 by ISSA, characterized as smooth and powdery with similar primary mineral sources and shapes as sand. Clay particles are defined as less than 0.002 millimeters in both systems, feeling sticky and plastic when moist, composed primarily of secondary clay minerals with a plate-like or flake-like shape. Soils that are easy to till are described as light, non-sticky, and less fertile due to low nutrient holding capacity, while difficult to till heavy soils are very sticky, plastic when wet, and possess a high nutrient holding capacity.

: Table 2 summary: Sands and clays differ fundamentally in their porosity, water retention, and aeration. Sands are characterized by low total porosity with more macropores, which leads to very good aeration but low water holding capacity, making them droughty. In contrast, clays have high total porosity with more micropores, resulting in high water holding capacity but poor aeration and drainage.

Figure 1 summary: A ternary diagram known as the Textural Triangle, which classifies soil types based on the relative percentages of clay, silt, and sand. The three axes represent the percentage of each component, with intersecting regions defining specific soil classifications such as sandy clay, loam, and silt loam. This tool allows for the precise identification of soil texture based on the proportions of its primary mineral constituents.

♦ The 12 Textural Classes

- The first three classes are classified roughly as coarse-textured soils

- Infinity Loam to silty clay loam are medium-textured soils

- infinity Sandy clay to clay are fine-textured soils

- ∞ Loam is the ideal texture for growing most crops because this class has nearly equal proportions of desirable properties attributed to sand, silt and clay

Soil texture determination

Table 3 summary: The twelve textural classes of soil, organized into three textural groups. The Sands group includes Sand, which consists of 85 percent sand or more, and Loamy sand, with 75 to 85 percent sand. The Loams group is the largest, containing Sandy loam, Loam, Silt loam, Silt, Sandy clay loam, Silty clay loam, and Clay loam. For example, Loam is defined as having less than 52 percent sand, 7 to 27 percent clay, and 28 to 50 percent silt. The Clays group includes Sandy clay, Silty Clay, and Clay, the latter of which contains 40 percent clay or more, less than 45 percent sand, and less than 40 percent silt.

1. Feel method

- ∞ rapid method which can be used in the field without the use of any elaborate instruments

- infinity qualitative method and can only approximate the soil texture

- infinity rubbing moist soil between the fingers and estimating the characteristic "feel" of the dominant soil separate in the soil

The word texture refers to the sensation when one rubs the material with the finger.

- ☐ Sandy soils will feel gritty and rough.

- Silty soils are smooth and powdery.

- Clayey soils are plastic sticky.

2. Roll method

- The moist sample is kneaded into a rod and the texture is approximated by the ability to form rods or of the rods to remain intact when bent into a loop.

- Infinity Sandy soils do not form rods.

- ∞ Medium textured soils such as loam and silt loam form rods but which break easily when a loop is formed.

- Clayey soils such as silty clay, sandy clay, and clay form a continuous rod and which can be molded into a ring without cracking or breaking.

3. Mechanical analysis (Hydrometer method and Pipette method)

- ^{infinity} uses the principle expressed by Stoke's Law of sedimentation which states that the settling velocity of soil particles in an aqueous medium is directly proportional to the square of their diameter multiplied by a constant

- infinity In equation, V equals K times D squared

- where V = settling velocity

- K = constant to correct for variations in

- temperature and viscosity of the soil suspension

- D = diameter of the particles, mm

The bigger the particle, the faster is the settling velocity.

- In a soil suspension where the soil separates (sand, silt, and clay) were dispersed, sand will settle first (after about 4 minutes) followed by silt, and lastly by clay particles (about 7 hours).

Hydrometer Method:

o Destroying the organic matter to remove the cementing material of the soil separates

Dispersing the soil vigorously with sodium hexametaphosphate

The suspension is made up to one liter in a Buoyoucous jar

○ A hydrometer is floated at specific time intervals

Soil structure

- ∞ refers to the clustering of the soil particles into characteristic aggregates of various sizes, shapes and stability

- the shape that the soil takes based on its physical and chemical properties

- infinity an unstable property

The nature of soil structure does not depend on the relative proportion of sand silt and clay because it deteriorates with poor soil and crop management.

Soil structure is affected by the kind and amount of cementing materials, the position of the soil in the profile, and by the management the soil has been subjected to.

- The greater the amount of cementing materials, the greater the aggregation and stability of soil structure.

- The major cementing agents in soil structure formation are colloidal clay, oxides of iron and aluminium (sesquioxides) and organic matter.

- o Humus binds particles together by virtue of its gel-like property.

- Decomposing organic matter produce by-products of microbial metabolism which act as cementing substances.

- o Fungi and streptomycetes produce mucilaginous substances that bind soil particles together.

- Calcium-rich (calcareous) soils are generally well granulated while sodium-rich (sodic) soils are highly dispersed

- infinity Structureless conditions

- o Little or no aggregation; the particles occur as single grains for example in sandy soils

- Compacted soils: the soil particles are bound together in large mass for example paddy soils

The best soil structure for good plant growth is the granular specifically, crumb structure because it has good distribution of large and small pores.

Laying mulch on the soil surface prevents destruction of the soil aggregates by raindrops as well as provides organic matter that can later be plowed under.

Infiltration is fastest where soil structure is granular or single-grained, moderate for prismatic or blocky and slow for massive and platy.

- infinity Sustainable soil management depends on how we manage good soil structure

Structural classes based on the shapes of the aggregates

1. Prismatic structure: pillar-like with level tops

2. Columnar structure : pillar-like with rounded tops; like prismatic structure, commonly occur in subsoils and in soils of arid and semi-arid regions

3. Blocky structure: cube-like and has more or less sharp edges and the rectangular faces are distinct

4. Sub-angular blocky structure: has edges which are more or less rounded; like the blocky structure, typical in clayey subsoils particularly in humid regions

5. Platy structure has disc-like aggregates; commonly found in virgin soils and subsoils; generally make the soil poorly drained 6. Spheroidal structure: rounded aggregates which are more porous; characteristic of surface soils especially those high in organic matter content

Granular / Crumb : resembles cookie crumbs; commonly found in surface horizons where roots have been growing

Table 4 summary: Soils with good structure are characterized by well-aggregated crumb, high total porosity, and low bulk density, which facilitate easy tilling and root growth. In contrast, poor soil structure is marked by massive or compacted soil, low porosity, and high bulk density, making it hard to till and restrictive to root growth. A key difference lies in pore distribution: good structure maintains a balance of macro and micropores for drainage, aeration, and water storage, whereas poor structure is dominantly micropores, leading to poor drainage and aeration.

♦ Soil pore spaces

- The micropores (small-sized pores) are formed within the aggregate; they store water.

- The macropores (large-sized pores) are formed in between aggregates; they drain excess water, provide aeration and root proliferation.

- As a medium for plant growth, a soil should have good proportion of the micropores and macropores.

fraction of the soil volume occupied by air and water

♦ Bulk density

- infinity the mass (dry weight) per unit volume of soil infinity Mathematically

Math summary: This expression calculates the bulk density of soil. It is computed by dividing the dry weight of the soil by the total volume.

- where: B.D. =bulk density in g/cm cubed

Math summary: This expression defines the oven dried weight of soiling and the total volume of soil clod in cubic centimeters. These components are used to determine the bulk density, which includes both solids and pore spaces.

- (includes solids and pore spaces)

- a measure of degree of compaction of the soil and an indicator of porosity

- The more compacted the soil, the greater is the bulk density value and the less porous it is.

- The range of bulk density values for sand and sandy loam soils is 1.20 to 1.80 g/cm.

- The range of bulk density values for clay, clay loam and silt loam is 1.0 to 1.60 g/cm.

Table 5 summary: Bulk density values and their soil interpretations. Normal soil is characterized by values between 1.0 to 1.3 grams per cubic centimeter. Values greater than 1.3 grams per cubic centimeter indicate compacted soil with poor soil structure, while values less than 1.0 grams per cubic centimeter indicate very loose soil.

Factors affecting bulk density

1. Soil texture

- The coarser the texture, the higher the bulk density and vice-versa.

- ∞ Sandy soils have higher bulk density because the particles tend to lie closer together; they are more closely packed

- Fine-textured soils such as silt loam, clay loam, and clay are generally well aggregated with large pores between aggregates giving low bulk density values.

- 2. O.M content: Higher O.M, lower B.D.

3. Cultivation

- If cultivation results in compaction, B.D. is higher.

- If cultivation results in loosening of soil, B.D. is lower.

4. Depth in the Profile

B.D. generally is higher with depth due to compaction brought about by the weight of overlying layers

Soils in the deeper horizons have higher bulk density due to their lower organic matter content, less aggregation, less root penetration.

Particle density

infinity mass (dry weight) per unit volume of soil excluding the pore spaces within that soil volume infinity In equation.

infinity In equation,

P.D. = Ws / Vs

where: P.D. equals Particle density in grams per cubic centimeter

Math summary: This expression defines the variables for calculating particle density. It specifies the oven dried weight of soil in grams and the volume of soil solids in cubic centimeters.

infinity Values of P.D. have a narrower range of 2.50 to 2.75 g/cm; Mean P.D. equals 2.65 g/cm

P.D. of a given soil is constant thus unaffected by fineness of the particles nor by the arrangement of soil colloids

P.D. may indicate the mineral ancestry of the soil

∞ High P.D. (greater than 2.70 grams per cubic centimeter) may indicate soils derived from heavy (iron-bearing) minerals (magnetite, hornblende, zircon)

infinity Low P.D. (less than 2.50 grams per cubic centimeter cubed) may indicate soils have high organic matter

Since organic matter is generally higher in topsoils than in subsoils, surface soils usually have lower particle density.

P.D. of organic matter is 1.20 to 1.50 grams per cubic centimeter

♦ Porosity

Porosity signifies the extent of pore space expressed as percentage of the bulk volume of the soil.

- infinity In equation,

- % Pore spaces = {1 - (B.D. / P.D.)} x 100

- The higher the bulk density of the soil, the lower is its porosity.

- ∞ As the bulk density approaches the value of the particle density, the percentage porosity approaches zero.

- If we can compact the soil to the extent that no pore space is left, B.D. will be equal to P.D.

♦ Aeration Porosity

- The volume of soil pore spaces left occupied by air after the other pore spaces are filled with moisture

- For upland/dryland crops, it is ideal that only about half of the total volume of soil pores be filled with water to let the plant roots to "breathe".

♦ Soil water

- Infinity constitutes the primary source of water for terrestrial plants

- ^{infinity} carries the ions and the solutes to plant roots where they can be absorbed

- infinity moves further in fine textured soils than in coarse textured soils

- Soil moisture that surrounds soil particles is held at varying degrees of tenacity.

- The farther away the moisture film from the surface of the soil particle, the weaker is the attraction between soil and moisture.

Soil moisture is held more tenaciously in fine textured soils because of the proximity of the predominant micropores present.

For the benefit of the plant growing on the soil, it is best to maintain the soil moisture content within the rootzone of the plants as close as possible to the upper limit of the available moisture range.

Soil Moisture Tension (S.M.T)

- the force by which water is held in the soil

- the force that must be overcome by plant roots to draw water from the soil

- ∞ expressed in atmospheres (atm) or bars, where 1 atm = 1.01325 bar; 1 bar = 0.9869 atm

- Tension becomes larger when the amount of water stored or retained is smaller.

- Infinity S.M.T is low in wet soils and increases as the soil dries up.

- Soil moisture moves from a zone of low S.M.T to a zone of high S.M.T, from wetter to a drier portion of the soil.

♦ Soil moisture - release curve

- A graph showing the relationship between moisture content and moisture tension of the soil, and the characteristic of the soil itself.

Calculations of Moisture Content (M.C)

i. Gravimetric. M.C by weight (M.C.w) ∞ the weight (or mass) of water per unit weight of soil in which it is contained infinity In equation, %M.C.w = [(F.W - O.D.W) / O.D.W] x 100 where:

% M.C.w = percent moisture content of the soil by weight

F.W = fresh weight of the soil, g

O.D.W = oven-dried weight of soil, g ∞ easily determined by oven drying the soil at 105 – 110 degrees Celsius for at least 15 hours to a constant weight

2. Volumetric. M.C by Volume (M.C.v)

∞ the volume of water per unit of bulk volume including soil solids plus pore spaces of the soil the conversion from M.C.w to M.C.v using the Bulk density of the soil (g/cm ^{3} ) is >%M.C.v equals %M.C.w times B.D.

3. Soil water Depth

infinity H sw equals M C v times H t

Where H t equals total depth of soil

♦ Availability of water at various moisture conditions

1. Water at saturation

All pore spaces are completely filled with water (maximum water holding capacity)

^{infinity} Occurs after a heavy rain and persists for only a short period of time ∞ S.M.T =0; the water in the soil is loosely held by the particles and it easily drips with the action of gravity

2. Water at Field Capacity (F.C)

An estimate of the upper limit of the available moisture range ∞ S.M.T = 1/3 bar; occurs when excess water has drained from the large pores after a period of saturation and only the water at the smaller pores is left

3. Water at Permanent Wilting Point (P.W.P)

an estimate of the lower limit of the available moisture range ∞ S.M.T = 15 bar; the point where the plant begins to wilt permanently because it can no longer draw up the very little moisture due to very high moisture tension

4. Hygroscopic (water) coefficient

the water film at the immediate surface of the soil particle infinity not available for plant use infinity held at a very high S.M.T of 31 atm

5. Available Water (A.W)

^{infinity} Computed by getting the difference between F.C and P.W.P, that is A.W = F.C - P.W.P

6. Gravitational water

infinity also called drainage water; the water which soon drains out of the macropores the difference between the water at saturation and the water at field capacity

Measuring soil moisture status

1. Gypsum blocks

- ∞ small cubes of gypsum connected to wires and buried at specified depths of the soil where water status is to be monitored

- The electrical resistance in a porous material like gypsum changes with the changes in moisture content.

- The block is calibrated so the electrical resistance is converted into moisture content (applicable from 1 to 15 atm S.M.T).

- It equilibrates with the moisture content in the soil when the block is imbedded in the soil.

- The gypsum block becomes wetter or drier as the water also does.

2. Tensiometer

- consists of a long tube filled with water and with a porous cup buried in the soil and a mercury gauge above the ground

- ∞ Water in the tensiometer equilibrates with that in the soil so that it moves in and out of the cup in response to changes in soil moisture content.

- The changes are read in the attached gauge.

♦ Water movement

1. Upward: Capillary movement of soil water

- infinity Capillary: movement of liquid through small channels.

- The forces involved are adhesion of water on the walls of channels, and cohesion which is the mutual attraction of water molecules with each other.

- The smaller the soil pores, the higher is the capillary rise of underground water

- Capillary pores in soil are not continuous but are broken by large pores.

2. Downward: Infiltration and Percolation

- infinity governed by gravitational forces

- Infiltration: the downward entry of water via the soil surface

- ∞ Percolation: the downward movement of water through the soil; the water moves at a greater depth in the soil profile

Soil Consistency

- the physical condition of the soil manifesting cohesion and adhesion forces acting within the soil at various moisture contents

- infinity the workability of the soil at specific moisture contents

- A soil behaves differently at different soil moisture content. It is hard when it is dry, friable when it is moist, sticky and plastic when it is wet, and viscous (flows like liquid) when super saturated

- Soil Moisture Consistency Limits or Atterberg Limits can be determined in the laboratory.

The manifestations of soil consistency are:

- Liquid consistency: the soil is easily puddled which is attained at paddy rice culture. Puddling destroys aggregation.

- Plastic consistency: the soil is plastic and sticky. It can be good for pottery.

- Friable consistency: Soil best for cultivation since it is soft, friable, mellow and soil structure is rejuvenated.

- Harsh/ hard consistency: the soil is hard and requires high energy to pull the plow, resulting to cloddy seed bed.

♦ Soil color

- infinity can be a useful indicator of the soil's identity and therefore its implicit properties

- Dark-colored soils are generally more fertile since the dark coloring is usually due to abundant humus content or parent materials (containing base-rich ferromagnesian minerals).

In general, reddish soils are very old soils which are acidic and low in basic cations.

- Infinity Red yellowish color in subsoils indicates good drainage.

- Dark bluish or grayish coloration (mottling) indicates poor drainage.

♦ Soil colordetermination

- Munsell Color Chart : the standard color comparison chart used

- Hue: the dominant spectral color

- o Value: darkness or lightness of color

- ☐ Chroma: gradation of purity of color or the intensity or brightness of a color

- infinity Example: 7.5 Y.R 4/6 Brown Hue equals 7.5 Y.R

Value = 4

Chroma = 6

Soil color of most soils is centered on the Brown color, the most dominant soil color of the lower soil horizon for example Brown, Reddish Brown, Yellowish Brown, Dark Brown

3. Chemical Properties of Soils

Chemical nature of soil constituents

Soil is considered to have 3 phases

1. Solid: organic and inorganic materials; serves as a skeletal framework of soils

2. Liquid: the soil solution which carries the dissolved nutrients

3. gas: soil air; composed mainly of N 2, O 2 and C-O 2

♦ Soil colloids

- infinity very small particles of matter (0.2 micron to 1 micron)

- infinity the seat of various chemical reactions in soils

- infinity with high surface area per unit amount (specific surface area)

- chemically reactive because of the electrical charges (positive and negative) on their surface

- infinity classified into 2 general group: organic colloids and the inorganic/mineral/clay colloids

Organic colloids

- infinity constituted by organic complexes occurring in colloidal form

- infinity represented by humus: a complex, high molecular weight organic product of the biological decomposition of organic residues in the soil

- Humus is relatively stable to further biological action

- The main source of negative charges in humus is the dissociation of H superscript plus from carboxylic and phenolic functional groups at high pH.

- Humus enables the soil to have greater ability to adsorb and exchange ions.

- The Basic structure of aluminum silicate clays

- o a tetrahedron which has a silicon atom at the center surrounded by four oxygen atoms at the corners

- a continuous network of these octahedron has aluminum, magnesium and other cations at the center surrounded by hydroxils at the six corners

- A layer of these octahedron make up the aluminum sheet ♦ Inorganic colloids (categories based on structure and chemical composition)

Image summary: A ball-and-stick diagram of a silicon-oxygen tetrahedron, featuring a central silicon ion (Si4+) bonded to four surrounding oxygen ions (O2-). This structure represents the basic building block of silicate minerals.

Image summary: A molecular diagram showing a central aluminum ion (Al3+) bonded to six surrounding oxide ions (O2-). The structure depicts an octahedral coordination geometry, illustrating how the aluminum cation is surrounded by six oxygen anions.

Image summary: A molecular diagram showing the arrangement of silicon (Si4+) and oxygen (O2-) ions. Each central silicon ion is bonded to four oxygen ions in a tetrahedral coordination. The structure depicts the basic building block of a silicate framework.

Image summary: A molecular diagram showing a crystal lattice structure composed of aluminum ions (Al3+), oxygen ions (O2-), and hydrogen ions (H+). Red bonds connect the central aluminum ions to surrounding oxygen ions, which are in turn bonded to hydrogen ions. This depicts the atomic arrangement and ionic bonding within an aluminum hydroxide or similar oxide-based material.

silica tetrahedron

alumina octahedron

silica sheet

octahedral sheet

1. Crystalline Silicate clays

composed of sheet-structured alluminosilicates of various types depending on the ratio of silica sheet to alumina sheet in the crystal structure

Infinity Examples are

○ 1:1 non expanding type (kaolinite and halloysite)

○ 2:1 expanding type or smectites (montmorillonite); most chemically reactive due to very high specific surface area

○ 2:1 limited expansion type (vermiculite)

2:1 non expanding type (Illite)

○ 2:2 type (chlorite)

Soils dominated by montmorillonite expand when wet and shrink when dry producing large cracks on the surface

2. Amorphous (non-crystalline) silicate clays

- infinity represented by allophone and imogolite

In the Philippines, they are usually associated with relatively young soils derived from volcanic ash and characteristically containing high organic matter.

3. Amorphous Non-silicate clays

Infinity occur as amorphous hydrous oxides of Iron and Aluminum Infinity Examples are

○ Hematite

Goethite o Limonite

○ Boehmite

○ Gibbsite

Electrical charges of silicate clays

1. negative charges

arise mainly from exposed hydroxyl groups at the broken edges of crystals arise when the H ^{+} of the hydroxyl dissociates especially at high pH or alkaline environment (pH dependent charges, mostly occurring in 1:1 clay types)

arise from isomorphous (same size) substitutions of ions in the silica or octahedral sheets (mostly occurring in 2:1 clay types)

∞ can be demonstrated by the positively charged organic dye, gentian violet which loses its color indicating its adsorption by the soil enables the soil to store nutrients, specifically the positively charged ions (cations)

The cations are adsorbed (attracted on surfaces of colloids) and kept from being washed away by water passing water through the soil solum.

Infinity Agriculture important soils are net-negatively charged.

2. positive charges

arise from the protonation or addition of H plus to O.H minus groups on the edge of minerals such as sesquioxides, allophone and kaolinite arise from the exchange of O.H minus groups for other anions can be demonstrated by the negatively charged organic dye eosin red which does not lose its color when it reacts with the soil

♦ Ion exchange

∞ a reversible process by which ions are exchanged between solid and liquid phases and between solid phases if in close contact with each other; occurs due to the presence of electrical charges in the soil infinity Two Types of Ion Exchange:

infinity Two Types of Ion Exchange:

Cation Exchange: the attraction of cations (positively charged ions) on the surface of colloids and exchanged for ions in the soil solution (N.H 4 plus, Ca 2 plus, Mg 2 plus, Na plus, H plus, K plus)

Anion Exchange: the attraction of anions (negatively charged ions) on the surface of colloids and exchanged for ions in the soil solution ( nitrate, phosphate, sulfate)

♦ Concept of milliequivalent and cmol

- infinity wt of 1 me equals atomic weight divided by the quantity valence times 1000

- infinity weight of 1 milliequivalent of K plus equals 39 divided by 1 times 1000 equals 0.039 grams per milliequivalent

- infinity wt of 1 me of calcium ion equals 40 divided by 2 times 1000 equals 0.02 grams per milliequivalent

infinity Sample calculations:

Calculate weight (g) of calcium ion 2 plus needed to replace 1 g of hydrogen ion plus

1 one milliequivalent of calcium ion 2 plus will replace one milliequivalent of hydrogen ion plus

1 me calcium ion equals zero point zero two grams; one me hydrogen ion equals zero point zero zero one grams

Using ratio and proportion, 0.02 grams divided by 0.001 grams equals x calcium ion divided by 1 gram hydrogen ion

Math summary: This expression solves for an unknown quantity of calcium ions. The result is twenty grams of calcium ions.

Using the concept of cmol

1 cmol = 1/100th of a mole

1 cmol calcium 2 plus equals 0.40 grams

1 cmol H plus equals 0.01g one half centimol calcium 2 plus will replace 1 centimol hydrogen plus

Math summary: This expression calculates the amount of calcium ions required for cation exchange in soil. It determines that twenty grams of calcium ions are needed based on a ratio where zero point zero two units of charge equals the input value.

Cation Exchange Capacity (C.E.C)

- the ability of the soil to adsorb and exchange cations with those in the surrounding soil solution as well as with the plant roots

- infinity the sum of all adsorbed cations per unit amount of soil

- commonly expressed as milliequivalent per 100 g of soil (me/100g) or cmol/kg soil

- infinity reversible, instantaneous, and stoichiometric process

- infinity typical values ranges from 10 me per 100 g to 30 me per 100g

- infinity increases with increasing amount of clay and organic matter

Cations are adsorbed on surfaces of colloids at varying levels depending on their valence, ionic size, hydration size, and concentration of cations.

- The greater the valence, the stronger the adsorption that is calcium 2 plus is more strongly adsorbed than potassium 1 plus

- The smaller the ionic size, the higher the ability of the cation to closely approach the colloidal surface

- The smaller the hydration size of the cation, the stronger is its adsorption capacity

- The greater the concentration of a particular cation in the solution surrounding the colloids, the more strongly adsorbed is that cation

- ∞ Generally, the adsorption strength is in the order: aluminum 3 plus and hydrogen plus are greater than calcium 2 plus, which is greater than magnesium 2 plus, which is greater than potassium plus, which is greater than sodium plus

In strongly leached soils, the more strongly adsorbed cations will be left in the soil.

Simple C.E.C Calculation

- infinity Simply add up the mes of all the cations adsorbed infinity Example:

A soil analysis showed that it contains the following cations. Compute for the C.E.C.

Exchangeable cations me/100g soil

Table summary: Exchangeable cations measured in milliequivalents per liter. Calcium is the most prevalent at 10.0, followed by magnesium at 6.0 and hydrogen at 5.0. Sodium and potassium are present in smaller amounts, at 1.5 and 0.5 respectively.

Math summary: This expression calculates the total exchangeable cations in soil. It sums the values ten point zero, six point zero, zero point five, one point five, and five point zero to reach a final result of twenty three milliequivalents per one hundred grams.

Percent Base Saturation (%B.S)

infinity the degree by which the exchange sites in the colloids are occupied by basic cations

The basic cations are calcium 2 plus, magnesium 2 plus, potassium plus, sodium plus, ammonium 4 plus, etcetera

infinity The acidic cations are H plus and Al 3 plus

○ Aluminum is acidic because it yields H plus upon hydrolysis.

infinity percent B.S is calculated by taking the ratio of the bases with the C.E.C

∞ Sample calculation: A soil analysis showed that it contains the following cations. Compute for the % B.S.

calcium ion 2 plus

magnesium ion 2 plus

K plus

sodium ion

H plus

aluminum ion 3 plus me/100g soil

10.0

6.0

0.5

1.5

5.0

4.0

Solution: %B.S = {me of bases/ C.E.C } x 100 %B.S = {(10.0 + 6.0 + 0.5 + 1.5)/27.0} x 100 = 66.7%

Exchangeable Sodium Percentage (E.S.P)

- infinity the degree by which the exchange sites of colloids are occupied by sodium ions

- )]), computed by taking the ratio of the me of Na+ and that of the C.E.C

- ∞ Sample calculation: In previous example, C.E.C equals 27 me per 100 grams of soil while sodium plus equals 1.5 me per 100 grams of soil

E.S.P = (me Na⁺/ C.E.C) x 100

E.S.P equals 1.5 divided by 27 times 100 equals 5.6 percent

The soil becomes highly dispersed with high E.S.P values ( greater than 15%).

- ∞ High E.S.P is undesirable because it leads to poor aeration and drainage or permeability to water.

♦ Soil pH

- the degree of acidity or alkalinity (basicity) of the soil

- infinity also referred to as soil reaction

- infinity determined by the relative abundance of H plus and O.H minus ions

- ∞ can also be expressed as pH equals negative log of the concentration of H plus or the negative logarithm of hydrogen ion concentration

The lower the pH value, the higher is the H plus concentration and the lower is the O.H minus concentration.

- infinity can be determined easily and quickly either using the pH meter or organic dyes

- infinity an indicator of soil fertility problem

Soil pH and nutrient availability

The most favourable pH for growing most agricultural plants is between pH 6 and pH 7 because at the availability of the nutrients and activities of beneficial microorganisms are at maximum at his range.

The range of pH in the Philippines is from pH 5.5 to pH 6.5.

infinity When the pH is too low (less than 5.0, strongly acidic)

○ nutrients particularly Ca, Mg, K, P, Mo, N become less available to plants

○ N release may also be hindered when the symbiotic nitrogen fixation and nitrification are inhibited

○ Fe, Al, and Mn become more soluble to the point of toxicity

○ P becomes complexed into insoluble forms with Fe and Al

P can also be precipitated as insoluble manganese phosphate compounds when the soil is rich in manganese oxides

Soils also become acidic when the bases are leached out and replaced by H superscript plus ions for example old soils in the humid tropics

Soil acidity may also develop from the decomposition of organic matter due to the formation of organic acids like fulvic acid, humic acid and carbonic acid.

When pH is too high ( greater than 8.0, strongly alkaline)

○ same nutrients become unavailable

- Most micronutrients (except Mo) become unavailable at high pH

- Iron deficiency commonly develops

○ P becomes complexed with calcium as precipitates of calcium hydroxyapatite or calcium phosphate dehydrate

○ K also competes with the now abundant Ca for plant absorption

Figure 2 summary: A diagram showing the availability of various nutrients and microorganisms in mineral soils across a pH range from 4 to 9. The width of each horizontal band represents the level of availability, with wider bands indicating higher availability. Fungi are most available at lower pH levels, while bacteria and actinomycetes, nitrogen, potassium, and sulfur peak at higher pH levels. Phosphorus reaches its maximum availability in a narrow range around pH 6.5 to 7.5. The figure illustrates that soil pH significantly influences the availability of different plant nutrients and soil microbes, with most reaching peak availability in the slightly acidic to neutral range.

Sources of Acidity

1. H plus and Al 3 plus ions (Hydrolysis of Al 3 plus indirectly contributes to soil acidity)

2. Carbonic acid (H 2 C O 3) dissociation:

Math summary: This expression describes the formation and dissociation of carbonic acid. It shows carbon dioxide and water combining to create carbonic acid, which then breaks down into two hydrogen ions and one carbonate ion.

- 3. Organic Acids from O.M decomposition

- Infinity Fulvic, humic and other inorganic acids are formed during organic matter decomposition

Production of C-O _{2} during organic matter decomposition is responsible for the lowering of pH of calcareous soils in submerged soils 4. Mineral weathering

5. Acid rain

6. Heavy cropping removes (crop removal) basic cations and replaced by H superscript plus ions from roots

7. Long-term use of acidifying fertilizers ( ammonium containing fertilizers) due to nitrification process (conversion of ammonium to nitrate and release of hydrogen ions in the soil)

Pools of acidity

1. Active acidity

- infinity acidity due to H plus ions in soil solution

- measured when pH is determined in the usual method of mixing equal amounts of soil and water

- infinity should be in equilibrium with reserve acidity

2. Reserve acidity

- infinite acidity due to H plus and Al 3 plus ions adsorbed on colloid surfaces

- ∞ also measured (in addition to active acidity) when K.C.l is mixed with the soil instead of water in the pH determination

Sources of Alkalinity

1. Base-forming cations

- As the basic cations such as Ca, Mg, K and Na saturates the soil's exchange complex, the H superscript plus ion concentrations in the soil solution will decrease and the concentration of O.H superscript minus increases.

- Infinity Alkaline reactions results from the hydrolysis of colloids saturated with basic cations

2. Carbonates (C-O 3 superscript 2 minus) and Bicarbonates H.C.O 3 superscript minus)

♦ Increasing the pH ( Liming)

- ∞ involves the application of lime: any Ca or Mg bearing compound added to the soil to neutralize the H+ ions

- infinity Lime reacts with carbonic acid to form bicarbonates which will dissociate with Ca replacing H plus in the exchange sites

- infinity Liming application: small amounts split and incorporated into the soil

- ∞ usually applied in large amounts (tons/hectare) ahead of planting to allow ample time to react with the soil

- ∞ its effectivity depends on the lime's fineness (particle size) and relative neutralizing value (R.N.V) or also calculated as the calcium carbonate equivalent (C.C.E)

- R.N.V: the strength of the lime in correcting soil acidity with reference to calcium carbonate; computed from the ratio of the molecular weight of calcium carbonate and that of the liming material,

R.N.V equals open parenthesis molecular weight of calcium carbonate divided by molecular weight of the limiting material close parenthesis times 100

- infinity Lime requirement: the amount of liming material needed to raise the pH of one hectare soil (2 x 10 superscript 6 kilograms) up to a desired level under field condition

- Too much limiting is can be harmful with the reduced availability of Fe, Mn, Cu, Zn, P, and B, and antagonism between Ca, K, and Mg.

Common liming materials

infinity these are the oxides, hydroxides and carbonates of lime

1. Limestone : made up chiefly of the minerals calcite calcium carbonate with R.N.V of 100%, or dolomite calcium magnesium carbonate 2 with R.N.V of 109%; Limestone deposits are crushed to specified particle size with average purity of 94%

2. Burned lime or quick lime C-A O or MgO: made by igniting calcium or magnesium carbonates; about 95% pure; hygroscopic, tends to absorb water from the air; cakes readily even when sealed in bags; C-A O R.N.V of 179%

3. slaked lime: hydroxide of lime made by reacting C-A O or MgO with water; about 95% purity; Ca(O.H) _{2} R.N.V of 136%

An R.N.V of 179% (C-A O) means that every kg of C-A O is equivalent in neutralizing ability to 1.78 kilograms of CaCO 3 .

The greater the purity, the greater the neutralizing ability of the lime

Calcium sulfate CaSO 4 also contains calcium, but it has sulfate which can form sulfuric acid.

∞ Gypsum is not a liming material, as it has very slight effect on pH, but can provide Ca as a nutrient or exchange with Na.

♦ Lowering the pH (acidification)

- infinity more difficult than raising the pH

- usually involves addition of large amounts or organic matter into the soil, or by adding ferrous sulfate or sulfur mineral [to transform into sulfuric acid]

Buffering capacity

- the resistance of the soil to drastic changes in pH

- The pH of the soil hardly changes because when the H superscript plus ions in the soil solution are leached out, these are replenished by the H superscript plus ions in the exchange complex (concept of active and reserve acidity); the replenishment is reversible making the coming a continuous practice in order to maintain the desired pH

- The higher the buffering capacity of the soil, the higher the amount of limiting needed to neutralize the acidity.

- The higher the C.E.C, the higher the buffering capacity.

- More lime is needed to raise the pH of acidic clay soils than acidic sandy soils.

♦ Acid sulfate soils

- infinity also found to occur in the Philippines

- The acidity is due to the oxidation of sulfur compounds in soils that are rich in sulfur, or are derived from sulfur-bearing minerals

- Infinity There is formation of sulfuric acid.

- Infinity pH value can be as low as 4.0

- Soil organisms of genus Thiobacillus also facilitate the oxidation of sulfur compounds to sulfate

♦ Saline soils

- soils with toxic amount of soluble salt content

- soils with electrical conductivity (E.C) greater than 4 mmhos/cm

- ^{*} occurs in arid areas where there can be evaporation of water reaching the area allows concentration of salts for example near sea coasts with sea water intrusion

- can be reclaimed by repeatedly flooding with fresh water

- infinity diversion canals must be constructed to prevent entry of salt water

Sodic soils

- soils with excessive amount of soluble sodium (Na content more than 15% of the C.E.C)

- infinity highly dispersed and poorly drained

- can be reclaimed by replacing Na⁺ in the exchange sites of colloids with Ca squared⁺ ( sources can be gypsum), and then washing out the Na⁺; for example application of gypsum

♦ Upland soils

- infinity also referred to as dryland soils

- infinity grown to crops like corn, vegetables, fruit trees, etcetera

- infinity aerobic most of the time

- ∞ the nutrients present in the soil exist in their oxidized state that is nitrate, hydrogen phosphate, sulfate, sulfate, iron three plus, manganese four plus, carbon dioxide

- soil color is brown, yellowish brown, or reddish brown

- organic matter decomposes with C-O 2 as a major product

♦ Lowland soils

- also referred to as paddy soils

- infinity grown to rice, and other crops requiring water or puddling

- infinity anaerobic most of the time because of continuous submergence

- There is a thin oxidized layer above the water surface.

- The nutrients exist in reduced state ammonium, hydrogen sulfide, manganese 2 plus, iron 2 plus, methane

- soil color is dark gray or bluish gray

- organic matter decomposes with the following major products: C H 4 (methane), H 2 S (hydrogen sulfide), organic acids, alcohols, and ketones

4. {Soil Organisms and Organic Matter}

♦ Soil organisms

infinity composed of large and small plants and animals

The larger organisms (insects, worms, moles, etcetera) prepare the organic materials for further degradation by breaking them into smaller pieces

The smaller organisms (bacteria, fungi, actinomycetes, algae, nematodes, protozoa) cause biochemical changes in the organic materials

infinity Roles:

o Responsible for biochemical changes o Agents in the decomposition of plant and animal residues

○ Improve soil structure through aggregation

Earthworm

- infinity eat detritus, soil organic matter and microorganisms found on these materials

- infinity also facilitates aeration and drainage through the channels they create

- infinity probably the most significant microorganisms in humid temperate region soils

- infinity 7000 species worldwide

- infinity Lumbricus terrestris and Allolobophora caliginosa are the most common

- infinity more numerous in fertile and alkaline soils than in infertile and acid soils

- infinity Epigeic: live in the litter layer, Ex. Compost worm – Eisenia foetida

- ∞ Endogeic: live in the top 10 to 30 centimeters of soil, Ex. Pale-pink-red worm – Allolobophora caliginosa

- Anecic: live in vertical burrow up to 1 meter, Ex. the introduced Night Crawler – Lumbricus terrestris

♦ Protozoa

- Single-celled animals (20 to 50 microns in diameter)

- infinity Aerobic

- infinity Ingest food through oral openings

- ∞ ingest other soil organisms particularly bacteria and helps released the immobilized nutrients in the bacteria

- infinity Reproduction: Binary fission; budding

- ∞ Population: 10 to the power of 3 through 10 to the power of 5 Cells per gram soil

- infinity Biomass: approximately 100 kilograms per H.F.S

infinity C.F.U: colony forming unit

H.F.S: hectare furrow slice

♦ {Bacteria}

infinity probably the most important in terms of their effect on soil properties

infinity involved in various nitrogen transformation, sulfur oxidation and reduction, and other chemical processes

infinity Morphological Grouping

o Cocci (speherical)

☐ Rods (short, long, curved)

Spiral (vibrio)

infinity Nutritional Grouping

Heterotrophic (O.M as source of carbon and energy)

○ Autotrophic

○ Photosynthetic (Energy from sunlight; C from carbon dioxide)

Chemosynthetic (Energy from oxidation of inorganic compound; C from carbon dioxide)

Grouping based on oxygen requirement ○ aerobic ○ anaerobic ○ facultative

∞ Grouping based on temperature for optimum activity ○ mesophilic ○ thermophilic ○ psychrophilic Population: 10 to the power of 6 10 to the power of 9 Cell per a soil

infinity Population: 10 to the power of 6 through 10 to the power of 9 C.F.U per gram soil

infinity Biomass: approximately 2,000 kilograms per H.F.S

Fungi

- infinity most adaptable and versatile soil organism

- some species can thrive in extreme acidity and alkalinity

- infinity able to decompose the resistant organic compounds such as lignin, cellulose, and gums

- ∞ Mycorrhizae : an association between fungi and plant roots which help plants in solubilization of P and its absorption

- Complex morphology (multicellular; highly branched)

- infinity Heterotrophic

- infinity Aerobic

- Acid-loving (efficient O.M decomposers under acidic conditions)

- infinity Population: 10 to the power of 4 through 10 to the power of 5 C.F.U per gram soil

- infinity Biomass: approximately 8,000 kilograms per H.F.S

Actinomycetes

- infinity attack and simplify complex organic compounds such as cellulose, chitin, and phospholipids

- infinity Branched mycelial structures

- infinity Intermediate between bacteria and fungi

- infinity Very fine hyphae (less than 1 micron diameter)

- infinity Heterotrophic

- infinity Aerobic : some microaerophilic

- Major Antibiotic Producer: Streptomycin, Erythromycin)

- infinity Acid Sensitive (Critical pH equals 5.5)

- infinity Population: 10 to the 5th minus 10 to the 6th C.F.U per gram soil

- infinity Biomass: approximately 4,000 kilograms per H.F.S

- infinity includes blue-green algae, green algae, and diatoms

- infinity Principally thrives in aquatic environment, loves moist habitat

- Infinity Both single-celled and multicellular species are present in the soil

- infinity Aerobic

- infinity Photoautotrophs

- Blue-Green Algae are capable of N 2 fixation

- infinity Excellent host for bacteria due to oxygenating capacity

- infinity Population: 10 to the power of 3 through 10 to the power of 5 C.F.U per gram soil

- infinity Biomass: approximately 250 kilograms per H.F.S

Soil Organic Matter (S.O.M)

refers to the totality of all carbon-containing compounds in the soil derived from either plants or animals

Organic constituents of plants:

○ Cellulose (15 – 60%)

Hemicellulose (10 to 30%)

○ Lignin (5 – 30%)

Water-soluble fractions: amino sugars, amino acids (5 - 30%)

○ Proteins

o Fats, oils and waxes

accumulation is affected by temperature, soil moisture, vegetation, soil texture, and cropping system

S.O.M is higher in areas of higher effective moisture regime. infinity most adaptable and versatile soil organism

some species can thrive in extreme acidity and alkalinity

infinity able to decompose the resistant organic compounds such as lignin, cellulose, and gums

∞ Mycorrhizae : an association between fungi and plant roots which help plants in solubilization of P and its absorption

Complex morphology (multicellular; highly branched)

infinity Heterotrophic

infinity Aerobic

Acid-loving (efficient O.M decomposers under acidic conditions)

infinity Population: 10 to the power of 4 through 10 to the power of 5 C.F.U per gram soil

infinity Biomass: approximately 8,000 kilograms per H.F.S

Actinomycetes

- infinity attack and simplify complex organic compounds such as cellulose, chitin, and phospholipids

- infinity Branched mycelial structures

- infinity Intermediate between bacteria and fungi

- infinity Very fine hyphae (less than 1 micron diameter)

- infinity Heterotrophic

- infinity Aerobic : some microaerophilic

- Major Antibiotic Producer: Streptomycin, Erythromycin)

- infinity Acid Sensitive (Critical pH equals 5.5)

- infinity Population: 10 to the power of 5 through 10 to the power of 6 C.F.U per gram soil

- infinity Biomass: approximately 4,000 kilograms per H.F.S

- infinity includes blue-green algae, green algae, and diatoms

- Infinity Principally thrives in aquatic environment, loves moist habitat

- infinity Both single-celled and multicellular species are present in the soil

- infinity Aerobic

- infinity Photoautotrophs

- Blue-Green Algae are capable of N 2 fixation

- infinity Excellent host for bacteria due to oxygenating capacity

- infinity Population: 10 to the power of 3 through 10 to the power of 5 C.F.U per gram soil

- infinity Biomass: approximately 250 kilograms per H.F.S

Soil Organic Matter (S.O.M)

refers to the totality of all carbon-containing compounds in the soil derived from either plants or animals

Organic constituents of plants:

○ Cellulose (15 – 60%)

Hemicellulose (10 to 30%)

○ Lignin (5 – 30%)

Water-soluble fractions: amino sugars, amino acids (5 - 30%)

○ Proteins

o Fats, oils and waxes

accumulation is affected by temperature, soil moisture, vegetation, soil texture, and cropping system

S.O.M is higher in areas of higher effective moisture regime.

More accumulation of organic matter in grassland than in forested land due to faster turnover of vegetative matter and shorter life cycle of grass than of trees

Cultivated soils contain an average of 2 to 3% organic matter.

Organic matter declines when the soil is cultivated because of the enhanced oxidation and microbial activity brought about by the loosening of the soil.

Effects of organic matter to soil properties

1. Physical

- infinity enhances soil aggregation and aggregate stability

- infinity reduces plasticity, cohesion and stickiness of clayey soils

- infinity increases soil water retention, infiltration rate, water holding capacity and aeration

- infinity darkens soil

- infinity reduces bulk density and compaction

2. Chemical

- infinity increases C.E.C of soils

- infinity increases soil buffering capacity

- ^{*} increases nutrient availability through solubilization of minerals by organic acids and by chelation of metal ions

- reduces Al toxicity by binding the Al ions in non-toxic complexes

- infinity increases soil native supply of N, P, S, etc

- adsorbs pollutants such as Pb, Cd and Cu

- infinity inactivates toxin and pesticides

3. Biological

- infinity provides C and energy to soil organisms and thus increases their diversity and activity

- infinity enhances microbial functions such as N fixation, decomposition, and nutrient transformations

S.O.M Decomposition

- Organic materials such as crop residues, animal manures and other carbonaceous and nitrogenous compounds are decomposed by the heterotrophic microflora in the soil.

- Decomposition is the enzymatic oxidation by soil organisms under aerobic condition with C-O 2 , heat or energy and water as the major products.

- in the process, soil organisms derive carbon and energy for their use

- essential nutrients like N,P and S are released for plant absorption

- anerobic soil organisms act upon organic materials under flooded conditions or in poorly drained soils

- Infinity toxic gases and organic acids produced may kill newly transplanted rice seedlings

- infinity Microbial Activity Related to S.O.M decomposition:

- o Fungi : unaffected by pH level

- Bacteria and Actinomycetes: inhibited at pH 5.5

Carbon/Nitrogen ratio

The carbon nitrogen ratio of organic materials is a convenient tool for predicting the rate of decomposition and regulating the quantity of mineral nitrogen available to plant.

The higher the C/N ratio (usually 30), the slower is the rate of organic matter decomposition because the nitrogen is immobilized by microorganisms. Soil microbes use whatever N is available, approximately 30:1 C/N

20/1 is the optimum C/N ratio of organic materials for faster decomposition; When the C/N ratio narrows (20) mineralization predominates and No 3 superscript minus levels increase.

Nitrogen-rich materials such as legumes or blood meal are metabolized very rapidly, and the micro flora responds little to supplemental nitrogen while the addition of ammonium or nitrate to straw or other nitrogen-deficient substrates greatly enhances decomposition.

C/N ratio of organic material is determined by analysis of the total C and N

← Microbial transformations of N

1. Mineralization: conversion of organic N to inorganic N; renders N available for plant use

2. Immobilization

- conversion of inorganic N to organic N; renders N unavailable for plant use

- ∞ happens when available N is used by soil microorganisms and assimilated it into their bodies

3. Nitrification

the biological formation of No 3 minus or No 2 from compounds containing reduced nitrogen

The most common initial substrate is N.H 4 minus and the final product is No 3 minus.

Two separate and distinct steps: 1st is initial oxidation of ammonium to nitrite, 2 superscript nd is the further oxidation of nitrate.

The production of nitrate is related to soil and solution pH values.

○ Optimum pH values may vary from 6.6 to 8.0 ○ Rate decreases below pH 6.0 and become negligible below pH 4.5

∞ Micororganisms responsible

- Nitrosomonas: chemoautotrophic, gram-negative, non spore forming, ellipsoidal or short rods, responsible for the oxidation of ammonium to nitrite

- Nitrobacter. chemoautotrophic, gram-negative, non-spore forming, short rods, further oxidizes nitrite to nitrate.

- Nitrate can be lost through denitrification and in leaching particularly in sandy soils, under heavy rainfall, or where excessive irrigation. Excess No 3 superscript minus leached from soil often ends up in ground water, lakes, and streams lead to water pollution such as eutrophication or the excess growth of plant and algae, and the health problem in infants and animals methemoglobinemia.

4. Denitrification

- biochemical reduction of nitrate-N to gaseous N by facultative anaerobic soil organisms ∞ Denitrificans reduce the nitrate to nitrite then to gaseous nitrogen forms, nitrous oxide (No) and elemental Nitrogen (N 2) that are commonly lost to the atmosphere ∞ Denitrification is all aerobic but nitrate is used as the electron acceptor in the absence of O 2.

The microorganisms involved: Pseudomonas, Achromobacter, Bacillus and Micrococcus ∞ a major avenue of loss of N in paddy soils and contributes to the low efficiency of applied nitrogen fertilizer

No 3 superscript minus in the thin aerobic surface of paddy soils is leached down to the reduced subsoil

5. Ammonification:

The process of ammonification is the result of the breakdown of organic matter such as dead animals and plants or waste materials like excrement.

∞ This breakdown is accomplished by microorganisms which utilize dead organic material for energy and produce ammonia and related compounds as a byproduct of their metabolites.

6. Symbiotic Biological N fixation

infinity renders N available to plants

^{*} occurs in legumes in the presence of rhizobia which are aerobic, gram-negative, non-spore-forming rods which are typically motile with simple nutritional requirement

Rhizobia enter and irritates the roothair causing the formation of root nodules the bacteria in root nodules trap atmospheric N which is transformed to N.H _{3} which will combine to organic compounds to form amino acids and proteins

In return, the plant supplies the carbohydrates and energy for bacteria's metabolism ∞ When the legumes are plowed into the soil, the fixed N is added into the soil.

7. Non symbiotic N fixation

conversion of atmospheric N amounting to 20 to 100 kilograms N/ha per year by microorganisms without an associated plant host the organisms include bacteria (Azotobacter, Beijerinckia and Clostridium pasteurianum) blue-green algae and some fungi species

Azotobacters are strict aerobes, mesophiles with an optimum temperature of 30 degrees Celsius, gram-negative, large cocci.

Members of genus Clostridium are anaerobes, gram-positive rods, which are found in soils with pH 5.0 and are still capable of growth at pH 9.0.

Infinity Clostridia proliferate when organic matter is added, and they often are numerous around plant roots.

Blue green algae (B.G.A) are believed to help maintain fertility of lowland rice paddies.

Common B.G.A in the Philippines are Anabaena uariabilis, Gloetrichianatans, Nostoc commune, Nostoccarneum, Hapalosophon sp., Anabaenopsis spp. and Tolypothrix sp.

♦ Inorganic P solubilization

infinity Genera of bacteria capable of solubilizing Calcium phosphates Pseudomonas

○ Mycobacterium

○ Bacillus

○ Micrococcus

infinity Genera of fungi capable of solubilizing Calcium phosphates ○ Penicillium ○ Fusarium ○ Aspergillus infinity Microbiological means by which inorganic P is solubilized

○ Production of organic acids

Nitric acid or sulfuric acid production

o Flooding resulting in the reduction of Fe in insoluble ferric phosphates

o Mycorrhizal association (related to organic production); Two general types:

- Ectotrophic : fungus forms a mantle around root exteriors hyphae enters into spaces between plant cells hyphae enters into spaces between plant cells examples (pine, eucalyptus)

- Endomycorrhiza : fungus penetrates the cells of the plants examples (orchids, coffee, fruit trees, rice and corn)

♦ Microbial transformation of sulfur

The major sulfur in soil is in the organic fraction with low concentration of sulphate, the form available for plants.

infinity Decomposition of organic S compound

○ Microbial assimilation or immobilization of S and their incorporation into microbial cells.

O xidation of inorganic compounds such as sulfides, thiosulfates and elemental S.

○ Reduction of S.O 4 superscript 2 minus and other anions to sulfides. In anaerobic conditions, sulfate availability may be limited in the soil.

Sulfate-reducing bacteria, predominantly of the genus Desulfovibrio and Desulfotomaculum use sulfate as the hydrogen acceptor in their energy-yielding metabolism, reducing sulfate to sulfide.

In aerated environments, the combined sulfur is ultimately metabolized to sulfate.

Members of the genus Thiobacillus are capable of oxidizing elemental sulfur to sulfate. They are gram-negative, non-sporulating rods which are predominantly aerobes.

The oxidation of elemental sulfur leads to the formation of enormous amounts of sulfuric acid which decreases soil pH.

Iron Precipitation by soil bacteria

- infinity brought about a group of bacteria sometimes termed as the iron bacteria

- )]), These transformations can be (a) Ferrous Oxidation from iron plus 2 to iron plus 3, (b) Iron Reduction, and (c) Iron precipitation from organic salt.

Composts and composting

- Composting: process of creating humus-like organic materials by piling, mixing, and storing of organic materials under conditions favourable for aerobic decomposition

- Compost: finished product of composting and used as soil conditioner or slow-release fertilizer

After composting, the C/N ratio of organic materials is reduced to about 14 to 20:1

Pathogenic organisms are destroyed during thermophilic stage (50 to 75 degrees Celsius) but heavy metals (inorganic contaminants) are not destroyed.

♦ Cellulose decomposition

- infinity Cellulose : one of the most abundant organic matter in nature

The genera of cellulose decomposing bacteria and fungi are the following:

○ Strongly cellullotic fungi are represented by species of the genera Aspergillus.

- Chaetomium, Cuvularia, Fusarium.

- Memnoniella, Phoma, Thielavia and Trichoderma.

- o A bacterial genus that contains representatives digesting cellulose includes Bacillus, Cellulomonas, Clostridium, Corynebacterium, Cytophaga, Polyangium, Sporoccytophaga and Vibrio).

- Bacillus: aerobic, spore-forming, gram-positive rods

- Cellulomonas : short gram-negative rods that produces yellow, water-insoluble pigments

- Clostridium: anaerobic, non-motile, gram negative rod, which does not ferment carbohydrates other than cellulose; produces a yellow pigment

- Cytophaga: aerobic, long, flexuous rod with pointed ends; abundant in soils receiving straw or manure

5. Principles and Management of Soil Fertility

♦ Soil fertility

- ∞ the capability of the soil to supply the nutrients in the right amounts and proportions to meet the nutrient requirement of the crop, as affected by soil properties and condition

- infinity only among the many factors that makes the soil productive

- infinity A fertile soil is not necessarily a productive soil.

Soil productivity

- ∞ the ability of the soil to support or produce a desired quantity of plant yield

- infinity A productive soil is necessarily fertile.

♦ Plant Nutrition

- infinity the supply and absorption of chemical elements or compounds required by the plant

- Infinity Roots absorb mineral nutrients as ions in soil water.

- Ions can be readily available to roots or could be "tied up" by other elements or the soil itself.

- Infinity Many factors influence nutrient uptake for plants.

- Nutrients: chemical elements or compounds required by plants for normal growth ✓ Metabolic processes: are mechanisms by which elements are converted to cellular materials or as sources of energy, or to drive reactions

The 17 Essential Elements

Carbon (C)

infinity major component of plant's organic compounds

2. Hydrogen (H)

major component of plant's organic compounds

3. Oxygen (O)

major component of plant's organic compounds

4. Nitrogen (N)

infinity Constituent of amino acids, proteins and nucleic acids D.N.A, R.N.A

Integral part of chlorophyll molecule

)]), Associated with high photosynthetic activity, vigorous vegetative growth, dark green color of leaves and succulence of tissues

5. Phosphorus (P)

Energy storage and transfer through A.T.P – A.D.P conversion

Structural component of nucleic acids, coenzymes, nucleotides, phosphoproteins, phospholipids and sugar phosphates

As constituent of A.T.P, P is involved in metabolic processes such as photosynthesis, respiration, synthesis of proteins, phospholipids, nucleic acids, lipids, cellulose, hemicellulose, lignin, pectin etc

Important in seed formation and development of reproductive parts of plants

Associated with increased root growth, early maturity particularly grain development

6. Potassium (K)

infinity Enzyme activator infinity Regulates osmotic pressure in roots

Maintains turgor pressure of guard cells and regulates opening of stomata, thus controlling photosynthesis and transpiration.

∞ Needed in A.T.P synthesis which is used in translocation of sugars from leaves, N uptake and protein synthesis.

Strengthens straw of grain crops and prolongs the life of the flag leaf.

Infinity Increases pest and disease resistance.

7. Calcium (Ca)

Infinity Enhances nitrate minus nitrogen uptake and regulates cation uptake

Essential for cell elongation and division

Calcium pectate in cell wall

8. Magnesium (Mg)

infinity Constituent of chlorophyll molecule

Structural component in ribosome which are associated with protein synthesis

infinity Associated with energy transfer reactions from A.P in metabolic processes like photosynthesis, glycolysis, T.C.A cycle, and respiration

9. Sulfur (S)

Infinity Needed in synthesis of sulfur-containing amino acids, such as cystine, cysteine and methionine

^{*} Needed in synthesis of coenzyme A, biotin, thiamin (or vitamin B.1 and glutathione

infinity Required for synthesis of chlorophyll

^{*} Occurs in volatile compounds responsible for the characteristic taste and smell of mustard and onion.

infinity Enhances oil formation in flax and soybeans Infinity Improves quality of forage by narrowing N/S ratio

Iron (Fe)

10. Iron (Fe)

infinity Chlorophyll synthesis and in enzymes for electron transfer

11. Copper (Cu) infinity Catalyst for respiration, enzyme constituent

12. Zinc (Zn)

In enzyme systems that regulate various metabolic activities

13. Manganese (Mn)

infinity Controls several oxidation-reduction systems, formation of O 2 in photosynthesis

14. Boron (B)

infinity believed important in sugar translocation and carbohydrate metabolism

15. Molybdenum (Mo) infinity In nitrogenase needed for nitrogen fixation

16. Chlorine (Cl)

. Chlorine (Cl) infinity Activates system for production of O 2 in photosynthesis

17. Nickel (Ni)

^{infinity} Component of enzymes urease and hydrogenase; involved in the mobilization of nitrogenous compounds

18. Cobalt (Co)

Essential for symbiotic nitrogen fixation

Criteria of Essentiality

1. Perform vital functions in plant metabolism that is plants cannot complete their life cycle in its absence or deficiency

2. Needed as integral part of plant structures and/or participates in one or more metabolic processes in the plant

3. No other element can substitute for that element if it is absent or deficient. The deficiency can only be corrected by the addition of that element

♦ Macronutrients : absorbed by plants in large amounts

1. C equals C O 2

2. H equals H 2 O, H 2

3. O equals O 2

4. N equals N.H 4 plus, No 3 minus

5. P equals H 2 P O 4 minus, H P O 4 2 minus, P O 4 2 minus

6. K equals K plus

7. Ca equals Ca 2 plus

8. Mg equals Mg 2 plus

9. S equals S O 4 2 minus

Micronutrients : needed by the plants in relatively low amounts

1. Iron equals Iron 2 plus, Iron 3 plus

2. Manganese equals manganese 2 plus

3. Cu equals Cu 2 plus

4. Zn equals Zn 2 plus

5. M 0 equals M 0 O 4 2 minus

6. B equals H 3 B O 3, H 2 B O 3 minus

7. Cl equals Cl minus

8. Ni equals Ni 2 plus, Ni 3 plus

9. C 0 equals C 0 2 plus

Mobile nutrients: the deficiency can be seen on older leaves

1. N

2. P

3. K

4. Mg

5. Zn

Immobile nutrients: the deficiency can be seen on younger leaves

1. Cu

2. Mn

3. Bo

4. S

5. Ca

6. Fe

Mechanisms of nutrient movement

1. Mass flow

- ^{infinity} nutrients are carried by mass movement of water as water is absorbed the roots

- the amount of nutrients absorbed depends on the amount of water and the rate of water flow to the roots and the concentration of nutrients in the water

- ^{infinity} believed to be the major avenue by which Ca, Mg, Zn, Cu, B, and Fe are absorbed

- ∞ low amount of nutrients are absorbed when absorption and transpiration of water by the plants is low

2. Diffusion

- the movement of ions from a zone of high concentration to a zone of low concentration

- infinity follows Fick's Law

- most nutrients particularly P and Ka re supplied to plant by diffusion

3. Contact exchange (interception)

- the direct exchange of ions between the toots and soil colloids as roots come in contact with the colloid

Carrier theory of nutrient uptake

- ∞ explained why certain crops for example sugarcane, root crops, oil crops, etcetera absorb more K than other cations

- infinity proposes that ions enter an outer space in the roots by diffusion

- a carrier energized by plant metabolism picks up the ion and carries it to the inner space of the roots

- ∞ after depositing the ion in the inner space, the carrier is ready to repeat the process

- infinity the first stage of diffusion is called passive uptake

- infinity the second stage is called active uptake which requires energy

♦ Difference between Passive and Active Uptake

1. Passive Uptake

- ^{infinity} Uptake is by diffusion and ion exchange, hence controlled by concentration and electrical gradient

- infinity non-selective process and not requiring energy from metabolic reactions in the cell

- )]), occurs outside the casparian strip and plasmalemma as a barrier to diffusion and ion exchange

2. Active Uptake

- transport of ions into the inner cells requiring energy due to the higher concentration of ions beyond the plasmalemma and into the cytoplasm which is against an electrochemical gradient

- The process is selective in that specific ions are transported by specific carriers

Nitrogen uptake

- infinity taken up as No 3 minus and /or N.H 4 plus but the nitrate is often the predominant form

- infinity N.H 4 plus is easily oxidized by bacteria in aerobic soil to No 3 minus as soon as N.H 4 plus appears

- No 3 minus uptake occurs against an electrochemical gradient or actively absorbed (energy requiring).

- infinity No 3 minus and N.H 4 plus uptake differ with pH of medium. ○ N.H 4 plus uptake is optimum at neutral pH and decreases as pH decreases.

- No 3 uptake increases with decreasing pH and decreases with increasing pH probably due to competition with O.H.

- N.H 3 is toxic to plant roots; it can penetrate cell membranes.

- The fertilizer Urea which is converted to N.H 4 positive by urease in soil can be taken directly by plants, though at slower rate than No 3

♦ Phosphorus uptake

- The active uptake is pH-dependent that is higher P uptake at low pH (4.0) than at high pH (8.7).

- P is readily translocated up and down plant and quickly assimilated into organic compounds.

Potassium uptake

- ∞ actively taken up in high rate by plant tissues even to the point of luxury consumption

- K is the only one essential nutrient cation which can be transported against an electrochemical gradient into plant cell.

- K in plant is very mobile with main transport direction towards the meristematic tissues.

- ✗ K uptake is high when plant is sufficiently supplied with N, with bulk of K uptake during the vegetative stage (in cereals, from tillering to ear emergence)

- ∞ K uptake and retention in plants are competitively affected by H plus, Ca plus plus, Mg plus plus and Na plus.

- Plants with enough amount of K have lower transpiration rate and require relatively lower amounts of water (more drought resistant) due to the lowering of the osmotic potential of cell sap, and the regulation of stomatal opening by the guard cells with the presence of K.

Calcium uptake

1. absorption is passive

2. Ca is largely immobile in the plant. Once deposited, it is not moved from older to younger leaves, but with the preferential direction is the shoot apex (actively growing parts). 3. Ca content of legumes is higher in dicotyledons than in monocotyledons and also higher in legumes than in other species

Magnesium uptake

i. Taken up in lower amount than Calcium 2. Competitive relationships: ammonium, K, Ca, Mn iii. Mg moves similarly as Ca in plant, except that Mg (unlike Ca) is mobile in the phloem; passive uptake in the transpiration stream.

♦ Sulfur uptake

1. Active uptake; absorbed as S O 4 2 minus ii. Translocation is mainly upward (acropetal).

3. Plant use atmospheric S as S 2 (sulfide) by absorption through the stomata.

4. S is also an important component of mustard oil.

♦ Yield response to increasing nutrient supply

infinity the growth curve is described as a Sigmoid curve the development of plants is initially rapid, exponential or quadratic [with increasing level of nutrients], then slows down and finally levels off ∞ crop yield increases as nutrient supply increases but the increment progressively becomes smaller for each succeeding increase in nutrient supply until further addition reduces yield infinity beyond the maximum yield is the zone of luxury consumption of nutrients

Liebig's Law of Minimum

Plant growth is limited by that nutrient present below the minimum requirement ∞ "By the deficiency or absence of one necessary constituent all others being present, the soil is rendered barren for all those crops to the life of which that one constituent is indispensable."

Mitscherlich's equation

infinity The equation: d y d x equals open parenthesis A minus Y close parenthesis times c where: D.Y = increase in yield

D.X = increase in input

A = maximum possible yield

Y = actual yield c= constant depending on the nature of x

If plants were supplied with adequate amounts of all nutrients except one, the growth is proportional to the amount of this limiting element which was added to the soil.

Plant growth increases as more of the element was added but not in direct proportion to the amount of the growth factor added.

The total increase in growth becomes less as increments of the growth factor increases.

♦ Growth Factors

1. Temperature

infinity temperature range for agricultural crops; 15 degrees Celsius to 40 degrees Celsius has effects on photosynthesis, respiration, cell wall permeability, absorption of water and nutrients, transpiration, enzyme activity, protein coagulation - Infinity optimum temperature is lower for photosynthesis than for respiration

- infinity increasing temperatures (0 degrees Celsius-60 degrees Celsius) increase absorption of water, nutrients and activity of soil organisms

2. Moisture supply

- ∞ water is needed to manufacture carbohydrates, maintain hydration of protoplasm, and for translocation of carbohydrates and nutrients

- ∞ low moisture level impairs nutrient absorption thru its effect on mass flow, diffusion and root interception

- infinity excess water impairs nutrient absorption due to respiration caused by lack of O 2

3. Solar Energy

- most plants grow best in full sunlight; Some are shade tolerant (e.g. black pepper, cacao)

- infinity high density plant cause shading

- infinity less shading in plants with more erect leaves

4. Soil Properties

- physical (texture, structure, bulk density, porosity, water holding capacity, hydraulic conductivity)

- chemical (pH, C.E.C, base saturation, salinity, toxic elements)

- infinity biological (O.M content and kind and amount of microbial population)

Soil Fertility Evaluation

1. Quantitative methods

- infinity Soil analysis

- Plant tissue analysis

- infinity Fertilizer Field Trials

- Pot experiments

2. Qualitative methods

- Nutrient deficiency symptoms

☑ Soil Analysis

- infinity Quick and precise methods of evaluating soil fertility status

- ∞ Principle: the amount of nutrient extracted by chemical reagents at any one time is the amount available throughout the growth period of the crop

- ∞ consist of taking soil samples properly, subjecting soil samples to chemical analysis, and interpretation of results

In making interpretations, the following are considered:

- o Kind of crops grown during the preceding 3 to 5 years

- ☐ The crop intended to grow

- o The kind and amount of fertilizer used

- o When was the soil last limed

- o The slope and extent of erosion

♦ Soil sampling

- Main objective is to collect a small amount of soil sample weighing about 0.5 kilograms that will represent the soil in a large area

- Infinity Accuracy of soil testing and the fertilizer recommendation depends largely on proper soil sampling

- Infinity Rooting habit of plants must be considered

- o Shallow rooted crops: samples should be collected from the surface layer (20 to 30 centimeters)

- Deep rooted crops: soil samples must be collected up to the subsoil

- Infinity Steps in proper soil sampling:

- Make a map of the farm showing the sampling areas.

- Collect spot soil samples from each sampling area

- o Take composite sample

♦ Plant Analysis

- The nutrient content in the plant tissue is related to the available nutrient supply of the soil.

- chemical laboratory analysis of the plant tissue is related to the available nutrient status of the soil on which the plant is grown

- ∞ fertilizer recommendations using this method become more reliable when correlated with the results of fertilizer field trials

♦ Fertilizer Field Trials

- assesses the effect of fertilizers and their interactions with all existing factors of crop growth and development in any given location usually in a farmer's field

- The resulting fertilizer recommendations are generally more realistic

Pot Experiment

- comparison of several fertilizer treatments including a control using small amount of soil in pots to have a better control of environmental factors

- infinity short duration under an artificial condition

- infinity preliminary in nature

Nutrient Deficiency Symptoms

infinity Requires skillful observation because the occurrence may be due to

○ insufficient amount and supply of soil nutrients ○ unavailability of forms of the nutrients present

no proper balance among different nutrient levels

♦ Fertilizer

- ∞ any substance that is applied to the soil or to the plantin solid, liquid, or gaseous form to supply one or more of the essential nutrient elements required for the nutrition and growth of plants

- infinity classified broadly into two organic and inorganic slash chemical fertilizers

Rationale for Fertilization

- the amount of available nutrients in the soil is not enough to meet crop management for high yield

- The nutrient in the soil is not present in readily available form.

- Nutrient depletion or loss is continuous

- There is an increase in crop production and farm income

Organic fertilizers

- ∞ any fertilizer product of plant and/or animal origin for example animal manures, green manures, compost that has undergone decomposition through biological, chemical and/or any other process as long as the original materials are no longer recognizable, soil-like in texture and free from plant or animal pathogens

- Pure organic fertilizer: no chemical has been added to the finished product to increase nutrient content.

- Fortified or enriched has been enriched with microbial inoculants, hormones or chemical additives to increase nutrient content.

- Examples of plant residues:

- Rice straw is one of the most abundant crop residues in the country and is usually used with animal manure in compost making.

- Corn stover can be composted but needs to be chopped further for faster decomposition

- – Ipil-ipil (Leucaena leucocephala) leaves with their high nitrogen content can also be used as green manure.

- Kakawate (Glyricidia sepium) leaves have more than 4% nitrogen content and can be applied to the soil directly as N fertilizer.

♦ Inorganic fertilizers

- infinity synthesized or are processed from mineral deposits

- ∞ any fertilizer product whose properties are determined primarily by its content of mineral matter or synthetic chemical compounds

- infinity contain one or more combination of the three primary elements, N, P, or K

- Single nutrient fertilizers: fertilizers that supply one primary nutrient; also called straight fertilizers; Examples: urea, ammonium sulfate

• Multinutrient fertilizers: fertilizers containing two or three primary nutrients; also known as: complex, compound and mixed fertilizers; Example: Ammonium phosphate (16-20-0)

○ Complete fertilizer: contains the 3 primary nutrients which are historically known to be deficient in most soils

♦ Conventional units of expressing fertilizer nutrients

- infinity Stated in either pure form or oxide form

- infinity Nitrogen is expressed as pure element N

- ∞ P and K are in oxides, P 2 O 5 and K 2 O

The nutrient content in fertilizers is written in percent N, percent P 2 O 5 and percent K 2 O in that order.

Common Nitrogen fertilizers

- ∞ Urea (45-0-0): highest N content among the solid N-fertilizers ( N H 2 ) 2 C-O; Hygroscopic and 100% soluble

- ∞ Anhydrous ammonia: with 82% N has the highest amount of N among all fertilizers; contained in pressure tanks and is usually custom-applied by injecting into the soil; Ammonia gas is basic, pungent and colorless

- Ammonium sulfate (20-0-0): hygroscopic and nearly 100% soluble; contains sulfur (~24%), recommended for S-deficient soils

- Ordinary superphosphate (O.S.P): contains 20% P 2O 5 ; Pelleted as grayish granules and has a faint acid odor; About 85% of the P is water soluble and it contains traces of other nutrient elements

- Triple superphosphate (T.S.P) : monocalcium phosphate monohydrate

Common K fertilizers

- ∞ Muriate of potash or potassium chloride (K.C.l) : highly soluble and contains traces of other elements

Fertilizer computations and recommendations

1. Fertilizer grade

- weight percentage of the nutrients contained in a fertilizer

- Infinity Guaranteed minimum analysis of the plant nutrient in terms of percent total N, percent available Phosphoric acid ( percent P 2 O 5 ) and percent soluble potash ( percent K 2 O )

2. Fertilizer ratio

relative proportion of each of the primary nutrients N, P 2 O 5 and K 2 O in a fertilizer material

- infinity Example: 14-14-14 equals 1:1:1

3. General formula:

Weight of fertilizer equals weight of nutrient divided by nutrient content

infinity Sample problem A

The fertilizer recommendation is 90-0-0

How many kg/ha Ammonium sulfate, A.S (20-0-0) must be applied to meet the recommendation?

Code summary: This procedure calculates the quantity of fertilizer bags required per hectare based on specific nutrient recommendations. It first determines the total mass of a fertilizer needed by dividing the target nutrient weight by the fertilizer's nutrient percentage. In multi-nutrient scenarios, it prioritizes the nutrient that is only available in one source to determine that fertilizer's mass, then calculates the remaining nutrient deficit to be filled by a secondary source. Finally, it converts the total mass into the number of bags by dividing by the bag weight, which is 50 kilograms.

Methods of fertilizer application

- ∞ Broadcast: when the fertilizer is spread evenly on the soil surface; suitable for rice crop since they are closely planted

- Band placement may be applied on the row below the seed level or slightly on the side of the seeds along the row; usually done for crops like corn, sorghum, tobacco, and fruit trees

- Foliar application: made when quick action of nutrients is desired or when certain micronutrients are needed to be supplied with the crop; usually

- employed in very plantations such as pineapple or banana

- In-the-row: fertilizer is applied along the bottom of furrow

- Ring: fertilizer is applied around the base of the plant or tree

- Hole: fertilizer is dropped in holes around the tree

- Spot. fertilizer is dropped in small amount on the side of each hill or plant

- Basal: first of fertilizer applied at planting time

- Topdress: application sometime after plants have emerged

- Fertigation: application of fertilizer dissolved in irrigation water

Considerations in choosing method of fertilizer application

- Relative mobility of nutrients in the soil

- infinity Type of crop and its rooting pattern

- infinity Soil texture

- infinity Season of the year

- infinity Kind of fertilizer

Time of fertilizer application

- infinity depends on climate, soil, nutrient and crop

- Infinity In sandy soils, N is necessarily split as well as K

- For heavy clays, all of N is sometimes placed at planting.

- P and K are usually applied at planting as they are less mobile, less subject to leaching and less soluble

- P is also needed at young age to accelerate root development

In alkaline soils, ammonium fertilizer is necessary deep placed to minimize volatilization of ammonia

6. {Soil Conservation and Management}

♦ Soil erosion

- ∞ the detachment and subsequent transport of soil materials (including rock fragments) by an agent (water, wind, or gravity) to an area of deposition

- an undesirable process in agriculture mainly because of the losses: soil + nutrient + water + water holding capacity

- Water is the most important agent of erosion in humid tropical areas and recognized as the major cause of land degradation in the Philippines

Mechanism of soil erosion

1. Detachment/dispersion: process by which raindrops splash soil sediments from the soil surface into the runoff; requires energy that is supplied by the kinetic energy of raindrops

2. Entrainment : transport of suspended soil particles from upslope to downhill direction whether in rills, between rills and in sheet flow

3. Deposition: process by which sediment settles out under the action of gravity; a selective process depending on particle size, being rapid for sand and slow for clay

Two General types of soil erosion

1. Geologic erosion

- infinity soil erosion at natural rate

- group of natural processes (including weathering, dissolution, abrasion, corrosion, and transportation) by which material is worn away from the earth's surface

- infinity the process of smoothing down the hills and mountains, etcetera

- Soil loss in natural vegetation = 1 millimeters/yr, but fairly matched with the rate of soil formation = 1 millimeters/yr

2. Accelerated erosion

- the removal of the topsoil faster than the rate of soil formation

- infinity approximated to be 10 millimeters per year

- infinity usually associated with human activities

Forms of soil erosion

1. Raindrop erosion : soil particles are detached due to the impact of raindrops and splashed at a longer distance in the downslope than in the upslope direction

2. Sheet erosion

- the uniform removal of thin layer or "sheet" of soil from the land surface by rainfall and surface runoff

- infinity the most widespread and probably the most damaging form of soil erosion

- ∞ recognized by the soil deposition at the bottom of a slope, or by the presence of light - colored subsoil appearing on the surface, or stones left on pedestals

3. Channel erosion

- infinity occurs where surface water has concentrated, so that a large mass of water supplies the energy both for detaching and transporting the soil

- infinity can exist as rill, gully, or stream erosion

- o Rill Erosion: an erosion process in which numerous small channels of only several centimeters in depth are formed; usually the result of water washing down between rows of cultivated crops that is planted up and down the hill or in implement marks and other slights and irregularities of the soil surface

- Gully Erosion: also known as advance rillerosion due to the increasing size of rills eventually leading to a gully or a channel too large for crossing by farm or to be smoothed out by ordinary tillage tools

- Stream Erosion: the carrying off of the soil material on the sides and on the bed of a permanent or intermittent stream

Factors affecting soil erosion

1. Climate

- Rainfall is the climatic element that mainly affects erosion in humid tropics

- ∞ Rainfall intensity (not rainfall amount) is positively correlated to soil erosion if all other factors are held constant

- Rainfall erosivity: the potential ability of the rain to cause erosion ∞ Downpours of high intensity and comparatively short duration invariably cause maximum runoff of lands subject to erosion

2. Relief/ slope

infinity slope steepness and slope length affect splash erosion and runoff behaviour by imparting velocity ∞ in longer slopes, the runoff water accumulates speed as it nears the bottom end of the slope infinity a long steep slope causes the most severe soil erosion

Land slopes cannot be directly changed but can be modified on their effect on runoff by the use traverse channels of terraces.

3. vegetation

infinity intercepts rainfall by absorbing the energy of raindrops, thus reducing runoff

infinity retards erosion by decreased runoff velocity infinity physically restrains the soil movement improves aggregation and porosity of soil by roots ad plant residue

infinity increases biological activity in the soil infinity its transpiration through the body tissues decreases soil moisture, resulting in increased storage capacity

4. soil properties

Soil erodibility: the soil's vulnerability or proneness to erosion which is influenced by infiltration capacity and structural stability of the soil infinity high clay content induces surface runoff and increases transportability but decreases detachability

5. Human activities

infinity include management practices and choice of cropping system infinity Farm practices contributing to soil erosion:

☐ shortening of fallow periods: more cropping period due to increase demand in food o Kaingin system of farming/ swidden agriculture/slash and burn

Monoculture system: planting of only one crop may have heavy demands for a particular nutrient

○ Overgrazing

Plowing along the slope of the land

Logging

Other practices such as; road construction, area development for housing and resettlement

On-site effects of soil erosion

effects of erosion from the farm where it occurs o Loss of soil and particle selectivity

- fine soil particles along with the nutrients are selectively removed

- the fraction of the coarse primary soil particles increases in the eroded area surface sealing and hardening

- soil particles are washed into the surface pores, forming a seal up to 1 centimeters thick which restricts water infiltration and increases water runoff - upon drying, the seal becomes a crust (a dense surface layer of soil particles) which impedes seedling emergence

Loss of nutrients/decreased fertility

- selective removal of abse0froming elements (K, Ca, Mg)

- nutrients attached to soil sediments are lost

- – dissolved nutrients are also lost in runoff

- added nutrients (fertilizers) are also washed away

Decreased soil depth

- – degrades soil as a medium for plant growth

- rooting depth is reduces

- thin topsoil, often mixed with the subsoil which is generally more acidic and less fertile

Off-site effects of soil erosion

∞ effects of soil erosion downstream where soil sediments are deposited; usually a consequence of the on-site effects

Siltation of irrigation dams, canals, paddy fields, etcetera

o Reduce life span of reservoirs

o Destruction of crops and animals downstream; buried crops adjacent bottomlands

o Destruction of infrastructure like bridges, roads and buildings

• sediment deposits raise the level of riverbeds reducing its capacity to hold water and increases the chances of overflowing; hazard to navigation

← extbf{Estimation of Soil Erosion} : (U.S.L.E) Universal Soil Loss Equation

- infinity Developed to estimate the rate of soil erosion under various conditions

- ∞ It can be a guide for selecting the most appropriate system and management practices that limit soil loss through erosion

alpha = 0.224 R times K times L times S times C times P

where: A = predicted rate of soil loss in tons/ha/year

R = rainfall erosivity index

K = soil erodibility factor

L = slope length factor

S = slope gradient factor

C = cropping system and management factor

P = erosion control practice factor

▶ R factor

- reflects climate(rainfall intensity and erosivity) as a factor of soil erosion

- infinity found in long term records of rainfall specific to each county or state

- ∞ determined by the total kinetic energy and the maximum 30-minute intensity of rain for a given time interval of a given rainstorm

♦ K factor

- reflects the fact that different soils erode at different rates

- ∞ the measure of rate of erosion per unit quantity of erosion for a specific soils determined using the standard erosion plot

- can be estimated using data of texture, organic matter, structure and permeability

♦ {L factor}

- infinity result of correlation studies of slope length and erosion using standard plots

♦ {S factor}

- )]), infinity shows the correlation of erosion to percent slope and slope gradient

C factor

- The C factor is the crop management factor and is the ratio of soil loss compared to fallow (bare, exposed) soil.

P factor

- The P factor is the erosion control factor expressed as a ratio of the soil loss with practices

- If a farmer plows up and down the slope of a hill, P=1. When plowing is done following the contours of the hill, P is reduced.

♦ {Tolerable soil loss (T)}

- T is the maximum level of soil erosion that will permit a high level of crop productivity to be maintained economically and indefinitely

Soil and Water Conservation Measures

1. Mechanical/engineering measures

- Terracing: involves construction of broad channels or benches across the slope to break the flow of runoff water; not a practical method for shallow soils

- ∞ Grassed waterways: refers to canals or channels planted with grasses to provide outlets for disposal of unavoidable runoff water

- Pond : a depression of considerable size located below the check dam to collect runoff

- infinity Check dam: a structure above the pond which retards runoff velocity

2. Biological/ Vegetative Measures

∞ Mulching

- the practice of covering the soil surface with crop residues

- o Mulches maintain a greater infiltration rate under prolonged erosive rainfall event by preventing the sealing off of surface soil pores

- Residue mulches are effective in reducing soil erosion because the scour forces of runoff are distributed among the mulch elements instead of acting entirely on the soil surface

∞ Cover cropping

○ involves planting of close-growing grasses and legumes to cover and protect the surface of the soil

- ☐ maintains and increases organic matter content and improves soil physical condition, suppresses weeds, and conserves water

- recommended cover crops: tropical kudzu, centrosema, calopogonium, guinea grass, para grass, napier grass, Alabang x

- may not be acceptable to small farmers because it gives no immediate income and the cover crop may compete with the main crop for water and nutrients

- Strip Cropping (Pilas-tanim) : refers to the growing of erosion-permitting crop and soil-conserving crop in alternate strips aligned on the contour

- infinity Crop Rotation (Ikot-tanim)

- ☐ the systematic planting of different crops in succession on the same piece of land

- general guide: grain crops such as corn and/or upland rice should be followed by legumes such as mungbean, soybean, and peanut

- allows the soil to renew the supply of nutrients which are preferentially depleted by specific crops

- ☐ advantages

- soil-building crops are distributed over all fields

- rotation provides for more uniform distribution of stable manure and fertilizer to all fields

- – well-planned rotations provide for more continuous cover

- soils are given time to recuperate from the effects of crops that may have extra-heavy demands for certain nutrients

- crops vary in the feeding range of their roots, therefore provides for more complete use of the soil profile

- rotation favors control of weeds, pests and diseases

- rotation results in a broader distribution of labor and income

^{infinity} Relay Cropping (usod-tanim)

○ involves the planting of two or more annual crops with the second crop planted after the first crop has flowered or nearing its harvest

the objective is to allow the second crop to make use of the residual moisture and to provide continuous ground cover to protect the soil from erosive rains throughout the year

○ Example: corn and sweet potato

∞ Multiple Cropping

- refers to a practice which increase crop productivity while providing better protection of the soil from erosion

- can be sequential cropping( growing of two or more crops a year in sequence) or intercropping and/or mixed cropping (growing of two or more crops on the same piece of land at the same time)

- Example: while sugarcane is still young, intercrop with mungbean, sorghum or corn

- infinity Alley Cropping (interhedgerow cropping)

- system where arable crops are grown in the alleys between rows of shrub/tree legumes which are pruned periodically to prevent shading and to provide green manure to the companion crops

- commonly used contour hedges are ipil-ipil, gliricidia, camachile (should be deep rooted compared to the main crop)

- ∞ High density planting : practice of increasing the population of the crop per unit of land area with due regard to the effect of crop competition

- Agroforestry : refers to the system of land management where woody perennials and agricultural crops are raised at the same time or sequentially

Cultural practices reinforcing soil and water conservation

1. Conservation tillage: broad term referring to the reduction of soil and water losses relative to conventional tillage; technically refers to a tillage system which leaves 30% residue cover after planting; Involves the following:

infinity contour cultivation

o plowing, harrowing and furrowing across the slope of the land

effective in minimizing soil erosion on gentle slopes reducing soil loss up to 50%

○ should be used with other conservation practices on areas with steeper slopes, high rainfall and erodible soils

infinity minimum tillage

☐ preparation of the seedbed with minimal soil disturbance

done with the use of herbicide or farm tools to remove weeds, followed by tillage to open only a narrow seedbed or hole where the seeds are sown

leaves the interrow areas untilled

• tillage, weeding and planting are carried out simultaneously to minimize exposure time of bare soil surface to the elements of soil erosion

mulch tillage: tillage practice that leaves a large percentage of residues (leaves, stalks, crowns, and roots) on or near surface as a protective mulch

- ∞ strip or zone tillage: preparation of seedbed by conditioning the soil along narrow strips in and adjacent to the seed rows

- ∞ subsoiling : practice of breaking up the hard pan below the plow layer to increase infiltration and to reduce runoff

- infinity ridge-tying

- the technique of connecting the ridges with cross-ties to form depressions for storing rainwater which is allowed to infiltrate later

- 2. correction of soil problems for example Liming

7. {Soil Survey and Classification}

♦ Soil survey

- an inventory of the soil resourcedescribing the characteristics of the soils in a given area

- infinity a Province is usually the unit of publication. Example: Soil Survey of Bohol Province

- classifies the soils according to a standard system of classification

- infinity plots the boundaries of the soils on a map; the map uses an aerial photo as the base

- infinity makes predictions about the behavior of soils

3 Elements of a Soil Survey

1. a map showing the geographic relationships of each soil

2. a text describing the soils 3. tables giving physical and chemical data and interpretations for various uses.

Map Scale : refers to how many inches on the map represents inches on the ground

Infinity Scale of 1 colon 24,000 says 1 inch on map equals 24,000 inch on the ground

Soil maps differ in their map scale

♦ Orders of Soil Survey

1. First order. very intensive (detailed); experimental plots, building sites; minimum size delineation is less than or equal to 1 hectare

2. Second order: intensive (detailed); general agriculture, urban planning; minimum size delineation is 0.6 to 4 has.

3. Third order. extensive; rangeland, community area planning; min. size delineation is 1.6 to 16 has.

4. Fourth order. extensive (reconnaissance); for broad land use potential and general land management; min. size delineation is 16 to 252 has.

5. Fifth order. exploratory; regional planning, national planning; min. size delineation is 252 to 4000 has

Soil Taxonomy : refers to the system of classification developed by the U.S.D.A Soil Survey with the following basic guidelines

1. Classify soils on basis of properties

2. Soil properties should be readily observable and / or measurable

3. Soil properties should either affect soil genesis or result from soil genesis

♦ {Reasons for classifying soils}

- infinity To organize knowledge about soils

- infinity To understand relationships among different soils

To establish groups or classes for practical purposes predicting behavior

○ identifying best uses

○ estimating productivity

☐ extending research results

✓ Levels of soil classification

e.g. Fine-loamy mixed, mesicAquicArgiudolls; Lipa series – from the town or landscape feature near where the soil was first recognized (Lipa)

1. Order

- Soil-forming processes as indicated by presence or absence of major diagnostic horizons

2. Suborder

- subdivision of soil order based on moisture and temperature regime

3. Great group

- infinity subdivision of suborder based on differences, arrangement, and degree of expression between soil horizons

4. Subgroup

- ∞ typical (central concept of the great group); intergrades or transitional forms to other orders, suborders, or great groups; extragrades or additional properties not common to great group characteristics

5. Family

- Properties important for plant root growth; broad soil textural classes averaged over control section or "solum"; mineralogical classes for dominant mineralogy of solum; soil temperature classes

6. Series

- a class of soils and the basic units used to classify soils; nearly 400 soil series in the Philippines

- parent material; kind, number and arrangement of horizons in the profile; kind and arrangement of horizons; color, texture, structure, consistency and reaction of horizons; chemical and mineralogical properties of the horizons

♦ Required knowledge in classifying soils

1. Diagnostic Horizons : distinct types of horizons that reflect nature of soil formation

2. Mineralogy: dominant type of clay minerals

3. Particle size distribution: proportion of coarse fragments (2 millimeters–74 millimeters size particles) in combination with fine fragments ( less than 2 millimeters size particles)

4. Temperature Regimes: mean annual soil temperature (Mat) measured at 50 centimeters from surface

5. Moisture Regimes: number of days when soil contains available water during the period when soil temperature at 50 centimeters below the surface is above 5 degrees Celsius

Diagnostic horizons: used for differentiating or classifying soil order level i. Diagnostic surface horizon: the Epipedon (Gr. epi, over, upon, and pedon, soil); a horizon that forms at or near the surface and in which most of the rock structure has been destroyed; upper horizon, not necessarily the A horizon only but may include B or part of B horizon

○ Mollic (L. mollis, soft): dark, soft, surface layer; thick, greater than 10 inches; high base saturation of greater than 50%; mineral soil; soils formed under prairie vegetation

Anthropic : like mollic but contains more than 250 ppm of citric acid soluble P 2O 5

○ Umbric (L. umbra, shade) : like mollic, but low base saturation

○ Historic (Gr. histos, tissue) : Organic soil (20 to 30% organic matter); saturated with water

Ochric (Gr. ochros, pale): thin, light colored surface layers that do not fit any of the above

Plaggen (Gr. sod, grass roots): man-made, surface horizon that is greater than 50 centimeters thick created by many years of addition of manure

Figure 3 summary: A diagram showing the relationships between three types of surface horizons. From a central Mollic horizon, arrows point toward Ochric, Histic, and Umbric horizons, labeled with the characteristics that differentiate them: thinner and lighter color for Ochric, more organic matter for Histic, and low base saturation for Umbric. The figure illustrates how these specific physical and chemical properties define the different surface horizon classifications.

2. Diagnostic subsurface horizon (or the lower horizons)

○ Argilic (L. argilla, white clay) : illuvial horizon of clay accumulation; Bt

○ Agric (L. ager, field) : has an accumulation of clay and humus to the extent of 15% of the soil volume

○ Natric (L. natrium, sodium) : same as argillic but with greater than 15% exchangeable sodium (Na); Btn

Spodic (Gr. spodos, wood ash): illuvial accumulation of oxides of Al and Fe (sesquioxides) and O.M; red or dark red color; only found in acid sandy soils; with high rainfall; generally found below E horizon; contains a Bhs or Bs horizon

Oxic : very weathered layer of only Fe and Al oxides and 1:1 clay minerals; low pH and not very fertile (found in tropical soils); Bo

Sombric: light-colored, low % base-saturation and well-drained

○ Placic (Gr. plax, flat stone): a thin, black to dark reddish pan cemented by iron, iron and manganese or by iron-organic matter complex

Duripan (L. durus, hard): subsoil cemented by silica

Fragipan (L. fragis, brittle) : subsoil that is hard when dry but brittle when moist

○ Albic (L. albus, white): light colored subsoil from where clay and free iron oxides have been leached out

degree Calcic: accumulation of calcium carbonate or calcium magnesium carbonate 2

Gypsic: accumulation of gypsum

○ Petrocalcic: cemented by calcium carbonate

Cambic : slightly altered layer; not weathered enough to be argillic; Bw horizon designation or development of color and or structure

○ None : no diagnostic subsurface horizon present

Soil Temperature Regimes are measured at 50 centimeters from ground surface

1. Pergelic: mean annual temperature (Mat) is less than 0 degrees Celsius

2. Cryic : Mat is 0 degrees Celsius to 8 degrees Celsius

3. Frigid : Mat is less than 8 degrees Celsius (warmer than cryic in summer)

4. Mesic : Mat is 8 degrees Celsius to 15 degrees Celsius

5. Thermic: Mat is 15 degrees Celsius to 22 degrees Celsius

6. Hyperthermic: Mat is greater than 22 degrees Celsius

∞ Prefix "Iso" is used if mean summer (June, July, August) and winter (December, January, February) temperature differ by less than 5 degrees Celsius

○ Isofrigid : Mat is less than 8 degrees Celsius

○ Isomesic: Mat is 8 degrees Celsius to 15 degrees Celsius

○ Isothermic: Mat is 15 degrees Celsius to 22 degrees Celsius

○ Isohyperthermic: Mat is greater than 22 degrees Celsius

Soil Moisture Regimes

^{*} measured in terms of the absence or presence of water held at a tension of less than 15 bars in the moisture control section by a period of one year soil moisture control section: 10 to 30 centimeters in clayey soils; 20 to 60 centimeters in loamy soils; and 30 to 90 centimeters in sandy soils

- aquic moisture regime: soil is saturated and no dissolved oxygen (reducing regime)

- aridic and torric: soil moisture control section is dry more than half the time when soil temp. at 50 centimeters is greater than 5 degrees Celsius; moist for less than 3 months only

- ustic moisture regime: dry for greater than 3 months and continuously moist for at least 3 months

- ☐ udic moisture regime : soil is dry for less than 3 months only

- × xeric moisture regime: soil is continuously dry 45 days after summer and continuously moist 45 days after winter (dry summer-wet winter)

The 12 Soil Orders: Each Order has a diagnostic epipedon and subsurface horizons; could be “none”

1. Entisol (ent, recent): very young soil showing very limited profile development; characteristically have A/C or A/R profiles, exhibit only ephemeral soil development; largely confined to surface horizon; may have an Ap horizon; 12.5% of world

2. Inceptisol (ept, inception): young soil with moderate profile development; shows the beginning of horizon development; little or no illuviation; soil formed in colluvial material

3. Aridisol (id, L. aridus, dry): limited change in parent material due to dryness; Arid regions of the world (19%), less than 10 in of rainfall, usually contain carbonates

4. Gelisol (el, no meaning): young soils with little profile development; presence of permafrost layer; remains at temperatures below 0 degrees Celsius for greater than 2 consecutive years; 8.6% of the world

5. Mollisol ( underline oll, L. mollis, soft ) : soils with thick, dark, soft surface; soils of the grassland

6. Andisol (and, no meaning): soils from volcanic ash and cinders; very light, low bulk density, early-stage secondary minerals (allophane, imogolite, ferrihydrite clays), High P fixing capacity; 0.7% of the world

7. Spodosol (od, Gr. spodos, wood ash) : acid sandy soils with thick E and red; Bhs, ochric and spodic; subsoil has accumulation of Fe and Al oxides, humus and amorphous clays

8. Alfisol (alf, no meaning) : argillic B horizon with high base saturation; fertile forested soils with ochric and argillic

9. Ultisol (ult, L. ultimus, last): the B horizon has high amount soft clay but low base saturation; soils more weathered than Alfisols

10. Oxisol ( ox , Fr. oxide) : highly weathered soil with B horizon containing mainly 1:1 Kaolinite clays

11. Vertisol ( ert, L. verto, to turn ) : shows large cracks upon drying due to dominance of montmorillonite

12. Histosol (ist, Gr. histos, tissue): organic soils; peat soils, organic material Peat: undecomposed to slightly decomposed organic matter in waterlogged areas; Muck: highly decomposed organic matter

Classification of soils into Land suitability classes

soils are classified according to their capability for agricultural use or non-agricultural use with a primary aim of protecting the soil from erosion and degradation the major considerations are the following:

risk of runoff and erosion

- o wetness or need for drainage

- limitations to root development and tillage operations for example shallow soil, low water holding capacity, salinity, presence of stones or boulders and climatic characteristics

♦ {9 suitability classes of soils}

1. Class A: good land that can be cultivated safe and extensively to most crops with ordinary good farming practices

2. Class B: good land which can be cultivated safely using easily applied conservation practices

3. Class C: moderately good land that can be used regularly for cultivated crops in good rotation but needs intensive soil conservation treatments

4. Class D: fairly good land that is best suited for pasture but which can be used for agricultural crops in good rotation provided intensive soil conservation practices are applied

5. Class L : land that is flat but is too wet or stony and therefore more suited to pasture or forestry

6. Class M: land that is too steep, eroded or shallow for cultivation of regular agricultural crops and is better left to pasture forestry

7. Class N : land that is very steep, eroded, rough, shallow or dry and is better suited to pasture forestry if handled carefully

8. Class X : level land that is wet most of the time and cannot be drained economically; best suited for ponds or recreational areas

9. Class Y: land that is too steep, eroded, barren and rugged and should be left for wildlife or parks

End of Soil Science

Review Questions in Soil Science

1. A dynamic natural body on the earth's surface composed of both living and non-living materials where plants can grow

a. Soil profile

b. Soil

c. Soil horizon d. Soil pedon

2. The study of soil from the standpoint of higher plants or plant production a. Petrology

b. Edaphology

c. Pedology

d. Physiology

3. The size of this soil particle is less than 1 micrometer.

a. Soil colloids

b. Silt

c. Sand

d. Organic matter

4. Nitrification carried out by autotrophic bacteria is not affected by which of the following?

a. Temperature

b. pH

c. Oxygen supply

d. Redox potential

5. In relation to crop production, clayey soils are known to be a. easy to cultivate

b. more fertile than sand

c. low water holding capacity

d. high percolation rate

6. A soil consists of the three components, namely: solid, liquid and gas a. the solid is composed of inorganic matter and organic matter

b. the liquid is a solution with dissolved ions in it

c. the gas component is about 80% nitrogen gas ( N 2 )

d. all of the above

7. This macronutrient is not a component of any organic molecule in the plant; its function is more catalytic in nature and usually deficient in coarse-textured soils. b. Phosphorus

c. Potassium

d. Calcium

8. Component of amino acids such as methionine, cystein, and cystine and is usually deficient in waterlogged soils.

a. Sulfur

b. Calcium

c. Magnesium

d. Copper

9. The soil is called a _ _ because it comes from the weathering of naturally occurring rocks and minerals.

a. Dynamic body

b. Natural body

c. Natural resource

d. Weathered rock

10. Needed in chlorophyll synthesis and usually deficient in alkaline soil.

a. Iron

b. Zinc

c. Molybdenum

d. Boron

11. Needed in the synthesis of auxin and is usually deficient in waterlogged soils.

a. Iron

b. Zinc

c. Molybdenum

d. Copper

12. Rocks formed by cooling and solidification of molten magma and lava in the crust a. Extrusive rocks

b. Igneous rocks

c. Sedimentary rocks

d. Intrusive rocks

13. Individual soil layers or layers parallel to the ground surface a. Profile

b. Pedon

c. Horizon

d. Solum

14. What is the moisture regime of the soil Tropaquepts which are Inceptisols that are found in the tropics?

a. ustic

b. aquic

c. aridic

d. xeric

15. The non-crystalline organic colloidal fraction of the soil.

a. Organic material

b. Humus

c. Clay

d. Silt

16. Soil microorganism that degrade carbon-containing pesticide are considered

a. Phototrophs

b. Chemotrophs

c. Heterotrophs

d. Autotrophs

17. The most abundant gas in the soil atmosphere is a. C O 2

b. O 2

c. N 2

d. Ar

18. The physicist who formulated the law governing the rate of settling particles in viscous medium a. Jenny

b. Dokuchaev

c. Lal

d. Stoke

19. Under its natural occurrence a soil is aggregated and porous.

a. An aggregate is composed of millions of individual particles GreenEmpire P.H (facebook dot com U.R.L) b. The pores are interconnected channels to other pores

c. Water and air occupy the pores

d. All of the above

20. Rocks that are formed when magma did not reach the earth's surface but solidifies in the cavities or cracks that the magma had made by pushing the surrounding rock apart or by melting or dissolving it.

a. Extrusive rocks

b. Intrusive rocks

c. Granitic rocks

d. Basaltic rocks

21. Loose earth materials above solid rock

a. Regolith

b. Solum

c. Pedon

d. Profile

22. Haplauents are young soils with minimal development. In what order does the soil belong?

a. Entisols

b. Inceptisols

c. Mollisols

d. Vertisols

23. The Philippine adopts the _ _ Soil Classification System a. United States Department of Agriculture (U.S.D.A)

b. Food and Agriculture (F.A.O)

c. International Society of Soil Science (I.S.S.S)

d. British Soil Classification System (B.S.C.S)

24. A soil horizon is defined as _ _.

a. The depth of finely divided soil mineral over bed rock

b. A soil layer that differs in recognized properties from other layers below

c. The slope of the soil surface relative to the horizon

25. Soil texture that would be best for growing lowland rice a. sandy loam b. clay c. silty loam d. silty sand

26. A sedimentary rock which is a recemented clay

27. A soil order characterized as shrinking and swelling dark clay soils a. Gelisols b. Vertisols c. Inceptisol d. Entisols

28. It is an amorphous or less crystalline clay developed from volcanic ash. a. Allophane b. Iron oxide c. Kaolinite d. Montmorillonite c. high percolation rate

d. all of the above

32. These are naturally occurring inorganic substances with fairly definite chemical composition and specific physical properties

a. Rocks

b. Igneous rocks

c. Primary mineral

d. Minerals

33. A soil order characterized as embryonic soil with few diagnostic features

a. Alfisols

b. Spodosol

c. Inceptisol

d. Entisols

34. In strongly acid soils, the availability of most micronutrient cations is a. Increased

b. Decreased

c. Not affected

d. Remains the same

35. Generally, fine-textured soils are characterized to have

36. The relative distribution of sand, silt, and clay is called soil _ _.

a. Texture b. Structure c. Cation exchange capacity d. pH a. Primary minerals

d. Tertiary minerals

38. Andepts are soils that were derived from volcanic activity and were originally classified as Inceptisols. What is the new order of these soils?

a. Gelisols

b. Andisols

c. Oxisols

d. Vertisols

39. It belongs to the 1:1 non-expanding type of silicate clay mineral.

a. Vermiculite

b. Illite

c. Kaolinite

d. Montmorillonite

40. The percent water remaining in soil 2 to 3 days after it had been saturated and the free drainage had practically ceased

a. Hygroscopic water

b. Permanent wilting point

c. Plant availability water

d. Field capacity

41. The study of rock

a. Pedology

b. Rockology

c. Petrology

d. Hydrology

42. Which of these soils has the most rapid percolation rate?

43. Soil texture refers to the coarseness or fineness of a soil

44. The primary source of calcium in the soil

a. Gypsum

b. Hematite

c. Shale

d. Calcite

45. An example of a 2:1 expanding type of silicate mineral.

a. Halloysite

b. Kaolinite

c. Illite

d. Montmorillonite

46. Most of the N in the solid fraction of the soil is in the form of

a. Ammonium N

b. Nitrate N

c. Nitrite N

d. Organic N

47. The molten mass where igneous rocks solidify from is:

a. Core

b. Magma

c. Mantle

d. Soil

48. The decomposition of the complex substances of rocks and minerals resulting to changes in chemical composition, release of soluble materials and formation of new minerals.

a. Exfoliation

b. Weathering

c. Chemical weathering

d. Physical weathering

49. The general term for the process whereby ions adsorbed on the surface of soil colloids are exchanged for ions in the soil solution.

a. Anion exchange

b. Cation exchange

c. Ion exchange

d. Isomorphous substitution

56. A subsoil with high clay accumulation is written in symbol as a. Bt b. Btc c. Ct d. Ct1

57. The source of permanent negative charge of clays. a. Anion exchange b. Cation exchange c. Isomorphous substitution d. Protonation

59. Microaerophilic microorganisms require a. Extremely high oxygen level b. No oxygen level c. Minimal oxygen level d. High oxygen level

60. The weathered parent material corresponds to this horizon a. A.B b. E c. C d. A.B.C

61. These are natural soil aggregates a. Pebbles b. Clods c. Peds d. Granules

62. A mean annual temperature of 8 degrees Celsius or higher but lower than 15 degrees Celsius defines this soil temperature regime a. Thermic b. Mesic c. Hyperthermic

d. Cryic

63. This compound reacts with carbonic acid forming a more soluble bicarbonate. Its reaction contributes to the weathering process. a. Hydration b. Hydrolysis c. Carbonation d. Solution

64. This horizon is plowed and rich in humus. It will be designated as _ _ horizon. a. Ap b. Bt c. Ct d. All of above

65. A 25 gram soil saturated with 5 me Ca ^{2+} has a cation exchange capacity equal to a. 5 me/100 g soil b. 25 me Ca/100 g soil c. 10 me Ca/100 g soil d. 20 me Ca/100 g soil

66. The principal form of nitrogen utilized during rapid plant growth period is a. N 2 b. N O 3 minus c. N H 2 d. N H 4 plus

67. The true soil corresponds to horizon a. A,B,C b. A,B,C,D c. C d. A,B

68. Characteristic soil structure of sandy soils a. single-grained b. massive c. plat y dot

d. crumb

69. In relation to crop production clayey soils are known to be

a. sticky to cultivate

b. fertile than sand

c. high water holding capacity than sand

d. all of the above

70. The mean annual soil temperature is 22 degrees Celsius or higher.

a. Mesic

b. Hyperthermic

c. Thermic

d. Cryic

71. A Russian pedologist who published the first soil forming factor equation

a. Lafinikov

b. Jennykov

c. Gerasinov

d. Dokuchaev

72. Compute the % base saturation of a soil with a C.E.C of 100 me/100 g and whose exchange sites are occupied by 20 me/100 g of basic cations.

a. 20%

b. 25%

c. 75%

d. 68%

73. The relationship of percent base saturation and soil pH a. %B.S increases as soil pH decreases b. %B.S decreases as soil pH increases c. %B.S decreases as soil pH decreases d. %B.S decreases does not affect soil pH

74. Particle density is a stable soil property and most agricultural soils would have particle densities close to this value a. 1.33 grams per cubic centimeter b. 2.66 grams per cubic centimeter

1.65 grams per cubic centimeter

fourth d. fifth b. 4th c. 3rd d. 5th

88. Soil formation slows down because of constant mixing within the profile, nullifying the colloid movement downward by a. Plant roots b. Burrowing animals c. Leaching d. Hydration

89. The lowest category of the U.S Soil Taxonomy is a. Order b. Subgroup c. Great group d. Series

90. The form of nitrogen taken up by plants from the soil. a. N O 2 b. N H 3 c. N H 4 positive d. N 2

91. What do you expect when you increase O.M of the soil? a. Decrease the amount of N to apply b. Increase the amount of N to apply c. Maintain the amount of N to apply d. None of the above

92. Calculate the gravimetric moisture content of the soil sample if its fresh weight (F.W) is 25 g and its oven dry weight (O.D.W) is 20 g. a. 10% b. 15% c. 20% d. 25%

93. The upper diameter size limit of clay particles is a. 2.0 millimeters b. 0.002 millimeters c. 0.2 millimeters d. 0.02 millimeters b. Desalinization d. Paludization

113. The highest category in U.S Soil Taxonomy.

a. great group

c. suborder

d. series

114. The microorganism responsible for the conversion of ammonium to nitrite.

a. Nitrosomonas b. Azotobacter c. Mycorrhizae d. Nitrobacter

115. Considered as zone of eluviation a. A.B b. E c. C d. A.B.C

116. This mineral is hardly soluble in water a. Talc b. Quartz c. Gypsum d. Fluorite

117. The ideal bulk density value of a soil

a. 2.33 grams per cubic centimeter

b. 1.33 grams per cubic centimeter

c. 1.65 g/cm cubed

d. 2.66 grams per cubic centimeter

118. The chemical migration of Al and Fe and/or organic matter a. Ferrugination b. Podzolization c. Laterization d. Gleization

119. The movement of material out of a portion of soil profile. a. Illuviation b. Leaching

c. Podzolization

d. Eluviation

120. Organic soils that exhibit or possess a histic epipedon belong to the order

a. Mollisols

b. Histosols

c. Oxisols

d. Ultisols

121. One of the following is immobile in plants

a. Nitrogen

b. Potassium

c. Calcium

d. Sulfur

122. This is not an element of climate

a. Relief

b. Precipitation

c. Temperature

d. Sunshine

123. The physicist who formulated the law governing the movement of water in the soil

a. Stoke

b. Dokuchaev

c. Darcy

d. Aristotle

124. Characteristic feel of sand separates when rubbed in between the finger is

a. Gritty

b. Floury

c. Sticky when moist

d. All of the above

125. Consists of sand in ridges and intervening troughs that shift with the wind

a. Beaches b. Duneland

c. Pits

d. Riverwash

126. These are microorganisms that can grow at high temperatures (45 ^{circle} C and 75 ^{circle} C).

a. Psychrophiles

b. Thermophiles

c. Pedophiles

d. Mesophiles

127. A combination of all the management and land use methods to safeguard the soil against depletion, loss and deterioration by natural and/or man-induced factors. a. Soil Science b. Pedology c. Soil Conservation and Management d. Universal Soil Loss Equation

128. Soil moisture and temperature regimes are commonly used in what category of the U.S Soil Taxonomy? a. Suborder b. Order c. Great group d. Family

129. The microorganism responsible for the conversion of nitrite to nitrate. a. Nitrobacter b. Azotobacter c. Mycorrhizae d. Nitrosomonas

130. Temporary unavailability of nitrogen in the soil because it is being used up by microorganisms to build their tissues. a. Ammonification b. Immobilization c. Mineralization d. Nitrification

131. Bio-N is a biofertilizer which enhances shoot growth and root development of host crop. Who developed Bio-N?

a. Dr. Erlinda Paterno

b. Dr. Bayani Espiritu

c. Dr. Reynaldo Ebora

d. Dr. Ida Dalmacio

132. Parent material deposited in lakes is referred to as

a. Alluvium

b. Marine

c. Lacustrine

d. Tuff

133. Identify the soil physical property that is not readily subject to change, so it is considered a basic soil property

a. soil structure

b. soil texture

c. bulk density

d. soil color

134. Soils with very little development. The profile properties are largely inherited from parent material.

a. Entisol

b. Vertisol

c. Aridisol

d. Mollisol

135. Characteristic feel of clay separates when rubbed in between the finger is

a. Gritty

b. Floury

c. Sticky

d. All of the above

136. Characteristic feel of silt separates when rubbed in between the finger is

a. Gritty

b. Floury

c. Sticky d. All of the above

137. Bacteria with flagella all around the cell, with one or two at each pore a. Atrichous b. Lopotrichous c. Amphitrichous d. Peritrichous

138. Residues of living things in all states of decomposition whose influence on the soil properties is very significant even if present in very small amount. a. Inorganic matter b. Organic matter c. Soil air d. Soil solid

139. The most abundant element in the earth's crust is a. Ca b. Ti c. Si d. N

140. A master horizon that shows accumulation or deposition of either clay, silt, salts or other materials is a. B b. C c. A d. R

141. Soil with high clay content and base saturation, fertile, not cracking and can support good crop growth is a. Ultisols b. Oxisols c. Alfisols d. Andisols

142. It is the conversion of organic to inorganic forms of nitrogen. a. Ammonification b. Mineralization c. Nitrification a. Entisol

b. Spodosol

c. Aridisol

d. Mollisol

150. Soils with friable surface horizons darkened by organic matter accumulations.

a. Entisol

b. Mollisol

c. Inceptisol

d. Aridisol

151. Which of the following is not a soil structure?

a. Clay

b. Crumb

c. Platy

d. Sub-angular blocky

152. The highest gas composition of soil air.

a. N 2

b. Ar

c. C-O 2

O 2

153. The element which contributes to phosphorus fixation at high soil pH.

a. Aluminum

b. Calcium

c. Iron

d. Manganese

154. Aside from neutralizing soil acidity, lime like calcium carbonate may also

a. Improve soil structure

b. Improve soil texture

c. Increase C.E.C

d. Both A and C

155. Fixation of elements usually converts the elements from available to unavailable forms. Which of these processes render the element from unavailable to available form? a. N.H 4 fixation

b. P fixation

c. N 2 fixation

d. K fixation

156. In the absence of O 2, nitrate is used by facultative bacteria as their electron acceptor; No 3 is therefore reduced and lost in the form of

a. ammonium ion

b. No 2

c. N 2

d. N

157. In flooded soils, nitrate undergoes reduction and lost as gas in a process termed as

a. denitrification

b. nitrogen fixation

c. nitrification

d. volatilization

158. During O.M decomposition, the released N is utilized by microorganisms for the formation of new cells. This process is called

a. mineralization

b. nitrification

c. immobilization

d. denitrification

159. The basic elements lost in weathering are

a. Fe, P

b. Ca, Mg

c. Zn, Mn

d. K, P

160. Soils that are described to be self-plowing because of the large cracks formed upon drying

a. Vertisol

b. Alfisol

c. Ultisol d. Oxisol

161. Soil densities and porosities are affected by soil texture and soil structure. Which of the following statement is true? a. Porosity increases with increasing bulk density b. Soil compaction increases bulk density c. Soil aggregation increases bulk density d. None of the above 162. P = P 2O 5 multiplied by _ _ a. 0.34 b. 0.43 c. 0.54 d. 0.45

163. The _ _ contains dissolved electrolytes, non-electrolytes, ions, etcetera a. Soil organic matter b. Soil solution c. Soil air d. Soil solid

164. The study of the mechanical behavior of soils. a. Soil physics b. Soil microbiology c. Soil chemistry d. Soil mechanics

165. The mineral matter component of soils makes up about a. 25% b. 30% c. 50% d. 45%

166. In soil profile description, soil coatings or cutains must be properly observed. Which of the following is a cutan name? a. iron coatings b. {Ferran} c. Slickensides d. Both a and c

167. Pedon is the smallest volume that can be observed for purposes of soil classification. What is its range of dimension?

a. 1 to 2 meters

b. 1 to 10 meters

c. 8 to 12 meters

d. 10 to 20 meters

168. Soil temperature regimes are classified based on the normal prevailing temperature of the site. If the temperature is usually greater than 21 degrees Celsius, the soil belongs to

a. Cryic

b. Hyperthermic

c. Thermic

d. Mesic

169. The element which fixes phosphorus at low soil pH.

a. Calcium

b. Aluminum

c. Magnesium

d. Potassium

170. The measure of alkalinity or basicity of the soil a. Acid saturation b. Base saturation c. C.E.C d. pH

171. Which of the following causes soil acidity? a. Green manuring b. Irrigation c. Leaching of bases d. Liming

172. Soils with high buffering capacity are generally those which are a. Sandy soil with low organic matter b. Clayey with high organic matter c. Sandy with high organic matter d. Clayey with low organic matter

173. Which of the following soil microorganisms is the most numerous in soils? a. Bacteria b. Fungi c. Virus d. Actinomycetes

3 times 10 to the power of 6 kilograms

2 times 10 to the power of 6 kilograms

6 times 10 raised to the power of 2 kilograms

178. The nutrient element that is easily lost and mostly required by plants. a. Nitrogen b. Phosphorus c. Sulfur d. Calcium b. Soil map

c. Fertility map

d. Topographic map

186. Soil color is described using hue, value and chroma. In the soil color notation 4 Y.R 3/6, the hue is a. A. 4 Y b. 3 c. 4 Y.R d. 6

187. In 10R 2/5 color notation, the value is a. 10R b. 2 c. 10 d. 5

188. Soil mineralogy is commonly used in identifying names at this category a. Order b. Great group c. Family d. Series

189. The ability of the soil to resist pH change a. Base saturation b. Buffering capacity c. C.E.C d. Neutralization reaction

190. Which of the following manures contains the highest amount of nitrogen? a. Bat b. Cattle c. Goat d. Poultry

191. In the list given below, identify the potential source of toxins in the soil. a. Sewer sludge b. Decomposing O.M

c. Soil microorganism

d. Plant roots

192. This soil category defines largely on the basis of physical and mineralogical properties importance to plant growth.

a. Subgroup

b. Soil series

c. Great group

d. Family

193. In continuous flooding such as in waterlogged lowland rice, there is a decrease in the availability of these essential elements.

a. Zn, S and Cu

b. N, P and K

c. Ca, Mg and S

d. C, H and N

194. Which of the following is called the white mica?

a. Muscovite

b. Illite

c. Montmorillonite

d. Kaolinite

195. The dark color of igneous rocks is usually caused by a. Ferromagnesian minerals b. Quartz c. Feldspar d. Calcite

196. Current record on the total numbers of Soil Orders as of 2009 a. 100 b. 47 c. 12 d. greater than 1000

197. Number of soil orders found in the Philippines, as of 2009 a. 11 b. 12 c. 7 d. 10

198. It refers to grouping of soils in an orderly manner so that their properties can be easily remembered a. soil science

b. soil classification

c. land suitability

d. soil topography

199. The process of classifying soil types and other properties in a given area a. soil science

b. soil classification

c. soil survey

d. soil map

200. Studies the field observable attributes of the soil within the various soil horizons and the description of the kind and arrangement of the horizons a. Soil Physics

b. Soil Fertility

c. Soil Morphology

d. Soil Taxonomy

201. Refers to the vertical cross sections of the earth which shows the different soil horizons a. soil profile b. horizon c. pedon d. polypedon

202. A collection of soil individual essentially uniform in differentiating characteristics and in arrangement of horizons a. Series b. Family c. Sub groups d. Great groups

203. A soil with a bulk density of 1.3 grams per cubic centimeter and a particle density of 2.60 grams per cubic centimeter will have a porosity of a. 50%

b. 25%

c. 5%

d. 75%

204. Bulk density is a good indicator of soil degradation a. Bulk density does not change with poor soil cultivation practices

b. Increasing bulk density indicates deteriorating soil physical condition

c. Decreasing bulk density indicates deteriorating soil physical condition

d. None of the above

205. Type of soil structure that is best for growing upland crops a. Crumb

b. Massive

c. Platy

d. Loam

206. The soil structure of a compacted plow soil is a. Platy b. Crumb c. Massive d. Loam

207. Which of the following is an igneous rock?

a. Granite b. Limestone c. Shale d. Sandstone

208. A mineral that is composed of S i O 2 a. Tourmaline b. Gypsum c. Quartz d. Apatite

209. Wind deposited parent materials a. Lacustrine b. Alluvium

c. Tuff

d. Aeolian

210. The major source of all P in soils a. Kaolinite b. Feldspar c. Dolomite d. Apatite

d. Apatite

211. Profile depths vary depending on what type of soil formation took place and what present material was the source or origin. What is the standard depth of profile used for description a. 1 m b. 1.5 m c. 2 m d. less than 1 m

212. Plowing or cultivation has a great impact on soil formation. Which horizon shows cultivation? a. Bt b. Ap c. R d. C

213. Calcite weathers easily and forms a thick solum usually high in clay content. If the soil exhibits shrinking and swelling, the order most likely is a. Inceptisol b. Mollisol c. Vertisol d. Oxisol

214. It is a material used to ameliorate acid soils. a. Fertilizer b. Gypsum c. Lime d. Manure

215. It is also called as burned lime. a. Calcium carbonate

b. C-A O

c. Calcium Magnesium Carbonate 2

d. Calcium hydroxide

216. The lime produced by hydrating calcium oxide is a. calcium carbonate b. calcium oxide c. calcium magnesium carbonate 2

d. Calcium hydroxide

217. One of the major gaseous products of O.M decomposition under anaerobic soil conditions.

a. O 2

5. C-O 2

c. C H 4

1. C H 3 C H 3

218. Which among the following does not form of endomycorizial association with fungi? a. Rice b. Orchids c. Corn

d. Coffee

219. The chemical element in dolomite that is not present in calcite is: a. Mg b. P c. Na

d. C

220. The primary mineral most likely to accumulate at the site of chemical weathering of granite is

a. Mica

b. Muscovite

c. Quartz

d. Clay

221. Soil textural classes are defined in terms of ranges in variation in a. Structure b. Weathering

c. Texture

d. Drainage

222. Properties and materials are intended to reflect features which are widely recognized as occurring in soils and which can be used to describe and define soil classes a. Polypedons

b. Epipedons

c. Diagnostic horizons

d. Sub surface horizons

223. Refers to the upper most soil horizons used in the description of diagnostic horizons

a. Polypedons

b. Epipedons

c. Diagnostic horizons

d. Sub surface horizons

224. A man-made surface horizon that is greater than 20 centimeters thick, created by years of manure accumulation a. Historic

b. Plaggen

c. Anthropic

d. Calcic

225. Which of the following is true?

a. dark or black color indicates high organic matter

b. dark or black color indicates that the soil is high in oxides of iron

c. dark or black color indicates that the soil is at oxidized state

d. all of the above

226. Which of the following is true?

a. reddish color indicates high organic matter

b. reddish color indicates that the soil is high in oxides of iron

c. reddish color indicates that the soil is young

227. A chemical element is considered essential if

a. It is taken up by plants

b. It is involved in metabolic functions in the plants

c. It makes the plants greener

d. All of the above

228. The physical state of the soil as it relates to plant growth is known as soil

a. Texture

b. Consistency

c. Tilth

d. Structure

229. Consists of maps that shows the distribution of soils, description of the soils, some recommendation as to their use and management, and general information of a particular area a. Soil survey report

b. Climate map

c. Topographic map

d. Soil map

230. Plants depend on the water stored in the soil.

a. the upper limit of available water is saturated moisture content

b. the upper limit of available water is hygroscopic point

c. the upper limit of available water is field capacity

d. all of the above

231. The reaction of a compound with carbonic acid a. Hydration

b. Oxidation

c. Carbonation

d. Exfoliation

232. It is defined as the capacity of a liming material to neutralize acids expressed as a percentage of the molecular weight of CaCO 3 .

a. Percent base saturation

b. Percent calcium carbonate c. Neutralization reaction

d. Relative neutralizing power

233. Soil fertility is the ability of the soil to supply nutrients i a. Sufficient and balanced amount b. Amounts above the optimum c. Readily available forms d. All of the above

234. Soil horizon with organic debris partially decomposed a. Oi b. Oe c. A d. E

d. E

235. The color of a soil indicates some chemical conditions. Which of the following is true?

a. dark or black color indicates high organic matter

b. reddish color indicates that the soil is high in oxides of iron

c. yellowish color indicates that the portion of lowland soil is at oxidized state

d. all of the above

236. Plants depend on the water stored in the soil a. the upper limit of available water is field capacity b. the lower limit available water is permanent wilting point c. available water capacity is field capacity minus permanent wilting point

d. all of the above

237. A running water deposit is a. Lacustrine b. Marine c. Alluvial d. Eolian

238. A loosening or scaling of rock surface a. Unloading b. Exfoliation c. Defoliation d. Weathering

239. An air dry soil weighs 15 grams. After oven drying, the weight became 12.5 grams. What is the moisture content of the soil?

a. 20%

b. 24%

c. 22%

d. 23%

240. Type of silicate clay composed of a framework of tetrahedra

a. Phyllosilicates

b. Cyclosilicates

c. Inosilicates

d. Tectosilicates

241. Which among these is not a soil moisture regime?

a. Aqui c underline

b. Ustic

c. Udic

d. Mesic

242. In map, the upper portion is usually indicating what direction? a. West

b. North

c. South

d. East

243. The element in the soil that reacts with the liming material during the process of neutralization.

a. Hydrogen

b. Magnesium

c. Calcium

d. Sodium

244. What is the approximate volume composition of a loam soil in a good tilth?

a. 25% solid and 75% pore space

b. 50% solid and 50% pore space

c. 75% solid space and 25% pore space

d. 40% solid and 60% pore space b. calcium ion with a positive two charge

c. H plus

d. aluminum ion 3 plus

271. This refers to organic and inorganic matter which are exceedingly small but have high surface area per unit weight or volume

a. Organic matter

b. Soil colloid

c. Soil solid

d. Soil texture

272. These cations are dominant in strongly acidic soils.

a. H and Al

b. H and Ca

c. Al and Ca

d. Ca and Mg

273. Movement of water in the soil is always from

a. higher to lower soil moisture content

b. higher to lower total potential energy

c. higher to lower soil moisture tension

d. all of the above

274. If soil moisture content is 40%, field capacity is 30% and permanent wilting point is 20%, the amount of available water in the soil is

a. 10%

b. 20%

c. 30%

d. none of the above

275. Occurs when the pore spaces are filled with water or at its maximum water holding capacity

a. irrigation

b. saturation

c. hygroscopic coefficient

d. mass flow

276. The fertilizer is broadcasted over a growing plant

a. Broadcasting

b. Top dressing

c. Side dressing

d. Bedding

277. The fertilizer is placed along or between the rows of crops

a. Broadcasting

b. Top dressing

c. Sidedressing

d. Bedding

278. A red soil is generally a. Basic

b. Acidic

c. Sodic

d. Saline

279. This describes the darkness or lightness of a soil color.

a. Intensity

b. Value

c. Hue

d. Chroma

e. Moderate

280. What type of erosion took place when soil which is washed away creating small channels that are still repairable?

a. Sheet

b. Gully

c. Rill

d. Splash

281. Given the following conditions, select the soil which is less erodible a. Clayey, steep but with full cover

b. Clayey, steep but with sparse vegetation

c. Sandy, steep but with full cover

d. Sandy, steep with sparse vegetation

282. The group of soil microorganisms which have the ability to photosynthesize. a. Algae

b. Fungi

c. Nematodes

d. Protozoa

283. The bacteria which lives symbiotically with the roots of legumes and are able to fix atmospheric nitrogen.

a. Rhizobia

b. Aspergillus

c. Mycorrhizae

d. Penicillium

284. The most widespread association between microorganisms and higher plants.

a. Associative N fixation

b. Mychorrhizae

c. Symbiotic N fixation

d. Rhizobium-legume association

285. Liebig's Law of the Minimum in effect states that plant growth and yield a. are limited by excess of a particular nutrient b. are limited by the absence of a nutrient c. are limited by excess of one nutrient d. All of the above

286. Poorly drained soils can result into

a. Increased ethylene content in the leaf resulting to yellowing and etiolation b. Increased incidence of root diseases c. Increased rooting density d. cannot be determined

287. When depicted graphically, the Mitscherlich's equation shows that with addition of a limiting nutrient a. Yield increase linearly b. Yield increases exponentially c. Yield increase but in decreasing increment d. None of the above

288. The soil depth from which plants obtain the major part of the water absorbed as turned

a. Solum

b. Effective rooting depth of plant

c. Regolith

d. Rhizosphere

289. Porosity, which is the total pore-space volume of soils

a. is the same for all soil

b. Is highest in fine-textured soils

c. Is highest in coarse-textured soils

d. Varies little with difference in texture

290. This cation is dominant in sodic soils

a. Calcium

b. Sodium

c. Potassium

d. Magnesium

291. When Applied Which of the Following Materials Increases the C.E.C of the Soil

a. organic matter

b. sand

c. silt

d. none of the above

292. Soil grown to corn is best cultivated to have a soil consistency that is

a. Hard

b. Friable

c. Plastic

d. Viscous

293. Lowland rice land is prepared to have a soil consistency that is

a. Hard

b. Friable

c. Plastic

d. Viscous

294. The following can occur when soil particles are washed into the surface pores, except one a. siltation

b. surface sealing

c. water infiltration is restricted

d. water runoff increases

295. The incorporation of leguminous plants during their

a. Organic farming

b. Green manuring

c. Recycling

d. Littering

296. Advocates the maximum use of compost and organic materials a. Organic farming

b. Green manuring

c. Recycling

d. Littering

297. Poorly drained soils have prominent a. Bluish gray mottles

b. Reddish concretion

c. Yellowish or reddish mottles

d. Greenish mottles

298. Determination of soil textural class of a soil by rubbing a sample of the soil in a moist to wet condition and observing how the soil develops a continuous ribbon when pressing between the thumb and fingers to indicate the amount of clay present.

a. Feel and roll method

b. Particle analysis

c. Sieve method

d. Hydrometer method

299. Given the following conditions, when do you expect to have run off or overland flow?

a. Infiltration rate is exceeded by rainfall intensity

b. Infiltration rate is higher than rainfall intensity c. Prevailing soil structure is massive

d. Both a and c

300. Soil conservation measures may be either agronomic or engineering. What is the other name for agronomic conservation measures?

a. Crop factor

b. Biological

c. Mechanical

d. Both a and c

301. This factor is related to human activities of controlling soil erosion and has a numeric value that can be reduced by contour plowing, etcetera?

a. P factor

b. C factor

c. K factor

d. Both a and b

302. A group of microorganisms which can produce antibiotic compounds that kill other microorganisms.

a. Bacteria

b. Nematodes

c. Actinomycetes

d. Protozoa

303. Which of the following is not part of the nitrogen cycle?

a. Mineralization

b. Fixation by rhizobia and other organisms

c. Disintegration of minerals containing N

d. Plant uptake

304. It refers to the influence of one adsorbed ion on the release of another from the surface of colloid.

a. Cation exchange

b. Complementary ion effect

c. Fixation

d. Synergism

305. This element(s) has a critical role in sugarcane fertilization because of its function in the synthesis of sugar a. All of below b. Nitrogen c. Phosphorus d. Potassium

306. Nutrient enrichment of lakes and other bodies of water that stimulate the growth of aquatic organism which leads to a deficiency of oxygen in the water body. a. Eutrophication b. Algal bloom c. Red tide d. Salinization

307. What is the greatest advantage of no-plow system of reduced tillage? a. Greater yields b. Less fertilizer required c. Reduced labor and operation costs d. All of the above

308. The available form of nitrogen which predominates under upland condition is a. Ammonium b. Nitrate c. Nitrite d. Microbial Biomass N

309. The reduced form of sulfur under anaerobic conditions in paddy soils is a. Hydrogen sulfate b. Hydrogen sulfite c. Hydrogen sulfide d. Hydrogen disulfate

310. Soil sunction in a saturated zone beneath a water table is: a. Greater than zero b. Less than zero c. Zero

d. 10,000

311. An iron-coating substance found in root nodules which controls the entry of oxygen into the bacteroid is called

a. Auxin

b. Leghemoglobin

c. Plastocyanin

d. Chlorophyll

312. Some of its species can be found in extreme environments, thus they considered to be the most adaptable and versatile microorganisms

a. Rhizobium

b. Azolla

c. fungi

d. actinomycetes

313. The ability of the root-nodule bacteria to cause nodulation of the host plants is called a. Ineffectiveness b. Pathogenicity c. Effectiveness

d. Host-specificity

314. In terms of nitrogen fixation, the most efficient biological nitrogen fixing system is

a. Symbiotic

b. Associative

c. Free-living

d. All of the choices

315. Nitrogen-fixing organisms possess this enzyme which reduces nitrogen gas into available form

a. Phosphatase

b. Nitrogenase

c. Nitrate reductase

d. Hydrogenase

316. N-mineralization results in the release of available N in the soil like a. ammonium b. nitrogen dioxide c. nitrogen gas d. Urea

317. The following processes are transformations of the N in the soil. Which is not a biological process? a. N 2 fixation b. Volatilization c. Nitrification d. Denitrification

318. Vermicompost is produced from the decomposition of organic materials by this soil organism a. Protozoa b. Earthworm c. Nematode d. Beetle

319. In magnitude and algebraic sign, the matric potential of soil water is equal to a. Soil suction b. Negative hydraulic pressure c. Soil water tension d. Positive hydraulic pressure

320. Plant wilting commences when _ _. a. Water flow into roots stops b. Water starts flowing from roots back into the soil c. Water flow into roots drops below transpirational loss d. Soil is at field capacity

321. Which one is not true if soil pH decreases a. fertility decreases b. availability of nutrients increases c. more H superscript plus ions in soil solution d. % base saturation decreases d. A, B, C, R

b. oxides of Fe and Al less than Kaolinite, Halloysite less than Illite, Montmorillonite less than Vermiculite less than Humus

341. Among the factors considered in U.S.L.E, which is the most difficult to manipulate?

a. L and S

b. R

c. K

d. C and P

342. The stable fraction of the soil organic matter that remains after decomposition.

a. Carbohydrates

b. Carbon

c. Humus

d. Organic matter

343. The inherent capacity of the soil to provide nutrients to plants in the right amount and proportion.

a. Nutrient supplying capacity

b. Soil fertility

c. Soil resilience

d. Soil productivity

344. The mechanism of nutrient absorption whereby dissolved nutrients go with the convective flow of water from the soil to the plant root.

a. Mass flow

b. Contact exchange

c. Diffusion

d. Root interception

345. Which of the following agro-environments would produce the

greatest amount of greenhouse gases?

a. Lowland rice land

b. Upland rice land

c. Sugarcane field

d. Corn field

346. Basic properties described in a soil profile.

a. Color, texture, stoniness, structure

b. Texture, bulk density, consistency c. C.E.C, O.M (%) content, B.S, B.D

d. Plasticity, structure, consistency

347. The exchange of energy in radiant form between the soil and the atmosphere goes on:

a. Only during daylight hours

b. Only during night

c. Continuously

d. Only during cloudy day

348. Among are the main characteristics of organic fertilizers except

a. low nutrient content

b. application in big volumes

c. high solubility

d. Slow release of nutrients

349. The cation exchange capacity of a soil is a measure of

a. The force of bonding between the soil and exchangeable cations

b. The negative charge of the soil neutralized by easily replaceable cations

c. The speed with which ions added to the soil solution become adsorbed on soil particle surfaces

d. Soil acidity and basicity

350. Among the following, the material with the highest cation-exchange capacity is

a. Vermiculite

b. Montmorillonite

c. Organic matter

d. Kaolinite

351. The excreta or manure of African night crawlers is called

a. Vermicast

b. Vermicompost

c. Organic compost

d. African manure

352. The regulatory body in the manufacture of fertilizer (inorganic and organic) in the Philippines is a. Bureau of Soils and Water Management b. National Food Authority c. Fertilizer and Pesticide Authority d. Department of Agriculture

353. The growth factor that ultimately limits plant growth a. Biotic factor b. Genetic factor c. Edaphic factor d. Environmental factor

354. The most critical nutrients in the Philippine soils are a. N and P b. Na and K c. Na and Ca d. Na and Mg

355. Nutrient uptake that requires energy is called a. Passive b. Active c. Inactive d. Fast

356. The topsoil usually refers to this horizon a. A.B b. A c. B d. R

357. The subsoil usually refers to this horizon a. A.B b. A c. B d. C

358. The government agency in charge of the survey and classification of soils in the Philippines a. Bureau of Plant Industry b. Bureau of Soils and Water Management c. Department of Agriculture

365. Mathematically described as the negative logarithm of H plus ion concentration. a. Dissociation constant b. pH c. pH buffer d. P C O 2

366. Soil acidity which refers to the H superscript plus ion in the soil solution a. Buffering capacity b. Reserve acidity c. Active acidity d. Base saturation

367. Soil acidity which include the aluminum plus 3 and hydrogen plus ions adsorbed on the surface of soil colloids a. Reserve acidity b. Active acidity c. Buffering capacity d. Base saturation

368. What is CaCO 3 equivalent of 100% pure C-A O? a. 100 b. 135 c. 95 d. 179

369. What is the formula of quartz? a. S i O 2 b. K A l open parenthesis M g comma F e close parenthesis 3 S i 3 O 10 open parenthesis O H close parenthesis 2 c. C a C O 3 d. C a M g open parenthesis C O 3 close parenthesis 2

370. This is the property of water that explains how water molecules interact with each other and explains why water molecules are attracted to electrostatically charged ions. a. Ionic bonding b. Oxygen bonding c. Covalent bonding d. Polarity

371. It is referred to as the circuit of water movement from the atmosphere to the earth and back to the atmosphere.

a. Hydrologic cycle

b. mass flow

c. evaporation

d. Precipitation

372. Soil under its natural occurrence is aggregated and porous.

a. The aggregates are composed of millions of individual particles

b. The pores are occupied by water and air.

c. The pores are interconnected channels to other pores

d. All of the above

373. Which of the following statement is true?

a. The solid is composed of soil separates called sand, silt and clay.

b. The solids stick or cluster together to form soil aggregate.

c. The diameter range of sand is 2.0 to 0.02 millimeters, silt is 0.02 to 0.002 millimeters and clay is less than 0.002 millimeters.

d. All of the above

374. A method of soil fertility evaluation whereby nutrients are known before a crop is planted.

a. Soil Test

b. Biological test

c. Plant analysis

d. Nutrient deficiency symptoms

375. It is also referred to as troubleshooting type of plant analysis. a. Prognostic b. Diagnostic c. Monitoring d. Predictive

d. Predictive

376. The most common biological test to evaluate soil f a. Use of deficiency symptoms b. Plant analysis c. Field fertilizer experiment d. Soil chemical analysis

377. Materials which are natural or synthetic in origin which when added to the soil can supply nutrients to the growing plants. a. Fertilizers b. Humus c. Minerals d. Organic manure

378. An 18-46-0 fertilizer material contains: a. 18% N and 46% P b. 18% N and 46% K c. 18% N and 46% K 2O d. 18% N and 46% P 2O 5

379. The guaranteed minimum amount of nutrients in a fertilizer material is referred to as a. Fertilizer mixture b. Fertilizer recommendation c. Fertilizer formula d. Fertilizer grade

380. The most preferred form of nitrogen fertilizer since energy can be saved in protein synthesis. a. Ammonium nitrate b. Complete fertilizer c. Ammonium sulfate d. Urea

381. Complete fertilizers normally supply the following combination of nutrients a. N.P only b. N.P.K c. All the 16 essential elements d. N.P.K.S

382. It is considered one of the "lime nutrients" a. Calcium b. Phosphorus c. Potassium d. Sulfur

383. A compound excreted by plant roots during the process of respiration which is one of the causes of soil acidity

a. Carbonic acid

b. Hydrogen

c. Carbon dioxide

d. Oxygen

384. The localized fertilizer placement wherein fertilizers are applied along the furrows prior to seeding or as strips on one or both sides of the row about 5 centimeters away and below the seeds.

a. Banding

b. Basal

c. Sidedressing

d. Topdressing

385. It is an inorganic fertilizer material which is also a source of sulfur. a. Ammonium phosphate b. Gypsum c. Muriate of potash

d. Urea

386. High-pH soil which has relatively low soluble sa exchangeable sodium. a. Acidic b. Saline c. Saline-sodic d. Sodic 387. The most important step in soil chemical test. a. Soil sampling b. Sample drying c. Reagent preparation d. Sieving

d. Sieving

388. A method of fertilizer application mostly adapted for orchard and ornamental trees. a. Foliar b. Mudball

c. Seed pelleting

d. Trench or perforation

389. The process of the N transformation in anaerobic paddy soils whereby N is lost as gaseous N 2 , No and N 2O . a. Denitrification b. Immobilization c. Nitrification d. Ammonium fixation

390. Nutrient antagonism means that reduced availability of absorption of a nutrient occurs _ _. a. When another nutrient is deficient b. When another nutrient is in equal amounts c. When another nutrient is excessive d. All of the above

391. Under strongly acid soil conditions, P complexed into unavailable form as a. Tricalcium phosphate b. Al and Fe hydroxyphosphate c. Zn phosphate d. All of the above

392. Which among the following cation has the lowest relative flocculating power? a. sodium ion b. potassium ion c. magnesium ion d. calcium ion

393. Which of this C/N ratio of organic materials will transform organic N and inorganic N? a. 40/1 ratio b. 22/1 ratio c. 60/1 ratio d. 5/1 ratio

394. Major product of the biological transformation of Nitrosomonas GreenEmpire P.H (facebook dot com U.R.L) a. Nitrate + Hydrogen + energy

b. Nitrite + Sulfur + energy

c. Nitrite + Hydrogen + energy

d. Nitrate + Sulfur + energy

395. A soil has a cation capacity of 10 me/100 g and the following compliment of exchangeable cations, the amount being expressed in me per 100g of soil: H = 3.0; Ca = 2.0; Al = 3.0; Mg = 1.0; Na = 0.25; and K = 0.75. The percent base saturation of this soil is:

a. 10

b. 40

c. 70

d. 50

396. In slightly acid soils such as in those with pH between 6.0 and 7.0, the two most abundant cations will probably be

a. H and Al

b. K and Na

c. Ca and Mg

d. Fe and Mn

397. An illuvial horizon in a soil is designed by the symbol

a. A.1

b. A.2

c. B.2

d. O.2

398. This agro-industrial waste is the most plentiful solid waste produced after extracting juice from sugarcane stalks and has potential to be a fertilizer material

a. mudpress

b. filter cake

c. bagasse

d. distillery slop

399. The removal of excess water from a waterlogged soil depends on the

a. difference in soil solution

b. force of gravity c. Atmospheric pressure d. Temperature

400. The C.E.C of the soil is 20 me/100g. If it has 8 me/100g H and the remaining cations are bases, what is the % B.S? a. 80 b. 40 c. 60 d. 50

401. Which soil property is not influenced by O.M? a. Bulk density b. Texture c. Structure d. Color

402. Which is the seat of chemical activities in the soil? a. Sand b. Salt c. Colloid d. Clay

403. Which has the highest pH dependent negative charges? a. Organic matter b. Illite c. Montmorillonite d. Kaolinite

404. The dominant basic cation in agricultural soil is a. Na b. K c. Mg d. Ca

405. A form of fertilizer that is applied through the leaves a. Commercial fertilizer b. Foliar fertilizer c. Organic fertilizer d. Inorganic fertilizer

412. This macroelement is a component of protein and chlorophyll and is most limiting element in crop production except for legumes a. Nitrogen b. Phosphorus c. Potassium d. Calcium

413. The relative ease by which a nutrient is supplied by the soil a. Soil productivity b. Soil fertility c. Nutrient availability d. Intensity factor

414. This macroelement is a metal component of chlorophyll and is deficient in acid upland soil a. Nitrogen b. Calcium c. Copper d. Magnesium

415. When nutrients are immobile, deficiency shows up first in which part of the plant? a. Stems b. oldest leaves c. youngest leaves d. senescent leaves

416. The fertilizer with the higher percent N a. Ammonium sulfate b. Anhydrous ammonia c. Urea d. Ammonium nitrate

417. This enzyme is needed to transform urea to ammonium carbonate in the soil. a. Carboxylase b. Anhydrase c. Urease

d. Papase

418. The weak acid form upon hydrolysis and subsequent reaction of urea in soils is a. Acetic acid

b. Carbonic acid

c. Uric acid

d. Silicic acid

419. The percent N, P 2O 5 , and K 2O in a fertilizer is _ _.

a. Fertilizer ratio

b. Fertilizer grade

c. Fertilizer recommendation

d. Fertilizer brand

A single-element or straight fertilizer: a. Complete fertilizer (14-14-14) b. Ammonium Phosphate c. Urea d. All of the above

421. The fertilizer nutrients that are generally applied all at planting (basal). a. N & P b. P & K c. N & K d. P & Ca

422. Enzyme in nitrogen transformation in legumes: a. Nitrogenase b. Dehydrogenase c. Decarboxylase d. Anhydrase

423. This ratio determines mineralization rate of organic matter. a. N/S b. C/N c. P/N d. N/K

424. This is an acid forming reaction of ammonium ion c. Prism-like d. None of the above

437. Pore-size distribution affects movement and retention of water and air in the soil. Which of the following statements is true?

a. Micropores are for water retention.

b. Macropores are important in drainage and root respiration

c. Macropores and micropores are equally important to root growth

d. All of the above

438. Bulk density is a good indicator of soil degradation.

a. Land preparation using tractor results to low bulk density

b. Bulk density does not change with poor soil cultivation practices

c. Increasing bulk density indicates deteriorating soil physical condition

d. Decreasing bulk density indicates deteriorating soil physical condition

439. Type of soil structure that is best for growing upland crops a. Massive

b. Granular or crumb

c. Platy

d. Single-grain

440. The reverse of oxidation and involves the gain of electrons a. Reduction

b. Oxidation

c. Hydration

d. Hydrolysis

441. The moisture content of an air dry soil is known as a. Saturation Point

b. Permanent writing

c. Field Capacity

d. Hygroscopic coefficient

442. The movement of water in the soil is always from:

a. Higher to lower soil moisture content

b. Higher to lower total potential energy c. Lower to higher soil moisture tension

d. All of the above

443. One of the following is an organic source of nitrogen.

a. Ammonium nitrate

b. Ammonium phosphate

c. Ammonium sulfate

d. Azolla

444. Under upland condition, this is the most preferred source of N because it leaves less acidity.

a. Ammonium nitrate

b. Ammonium sulfate

c. Potassium nitrate

d. Urea

445. A method of fertilizer application whereby the materials are dissolved in water and applied as sprays to the foliage of the plant.

a. Foliar

b. Topdressing

c. Seed pelleting

d. Trench/perforation

446. This phosphate fertilizer is manufacture by the reaction of apatite with sulfuric acid and water.

a. Ammonium phosphate

b. Complete fertilizer

c. Ordinary superphosphate

d. Triple superphosphate

447. A phosphate fertilizer manufactured by reacting the superphosphate with ammonia.

a. Ammonium phosphate

b. Complete fertilizer

c. Ordinary superphosphate

d. Triple superphosphate

448. The form of soil potassium fixed within clay minerals such as illite and vermiculite. a. Slowly available b. Mineral K c. Readily available d. Relatively unavailable

449. One of the materials below is not a source of calcium. a. Epsom salt b. Calcite c. Dolomite d. Gypsum

450. This is one of the most common sources of magnesium. a. Calcite b. Epsom salt c. Gypsum d. Pyrite

451. The form of potassium that is present in the soil solution. a. Mineral K b. Relatively unavailable c. Readily available d. Slowly available

452. At same level of O.M which will have the highest water holding capacity? a. Loamy sand b. Clay loam c. Clay d. Sandy loam

453. The capability of the soil being molded by hands is a. Stickiness b. Tilth c. Plasticity d. Cracking

454. A soil chemical property which largely controls nutrient availability and microbial activities a. buffering capacity b. cation exchange capacity c. soil pH

d. electrical conductivity

455. Indicates excessive level of nutrient in the plant or soil a. Sufficiency b. Toxicity c. Deficiency

66. The most appropriate soil management whi availability of adsorbed P in acid upland soil a. fertilizer application b. prolonged anaerobic conditions c. organic matter application d. liming

457. A term that indicates low level of nutrient elements in plant or soil a. Sufficiency b. Toxicity c. Deficiency d. Poverty adjustment

458. The essential element that functions as a constituent of energy transfer metabolites a. Potassium b. Phosphorus c. Sulfur d. Magnesium

459. Which of the following is not an essential element to plants? a. Carbon b. Hydrogen c. Molybdenum d. Vanadium

460. These elements are micronutrients and are required by plants in small amounts a. N, P and K b. Cu, Mn and S c. Cu, Mg and S

461. Essential elements derived from air and water a. C, O, and H b. C, H and S c. N, C and H d. N, C and S

462. Which of these elements is available to plants in anionic form? a. Ca b. Mg c. P d. Fe

463. The micronutrient involved in the translocation of sugar in plant a. Copper b. Potassium c. Calcium d. Boron

464. The process that renders P available to plants a. Fixation b. Nitrification c. Solubilization d. Ammonification

465. A physical effect of lime a. Increase the cation exchange capacity b. Increase decomposition of organic matter c. Increase water holding capacity of soil d. Increase P availability

466. A term for the initial application of fertilizer for crops a. basal application b. top dressing c. side dressing d. band application b. Calcium sulfate

c. Magnesium chloride

d. Magnesium sulfate

468. The amount of lime to be applied to the soil in order to increase its pH

a. Fertilizer recommendation

b. Analysis grade

c. Lime requirement

d. Relative neutralizing power

469. It is a mixture of animal excreta and soiled beddings that accumulates in stables or barns

a. Compost

b. Green manure

c. Farm manure

d. Poultry manure

471. Which of these elements is available to plants in cationic form? a. Potassium b. Sulfur c. Chlorine d. Molybdenum

472. Soil loss through erosion can be calculated by the a. Mitscherlich's equation b. Universal soil loss equation c. Einstein's relativity equation d. Trigonometric equation

a. Fungi are less numerous than bacteria b. Fungi build up large biomass in the soil because of their filament networks c. Fungi can survive even at extreme pH conditions

c. Percolation

d. Capillarity c. Stoke's Law

d. Dalton's Law

486. The pore spaces meant to retain moisture are

487. A soil condition when fine particles clog the pore spaces which may not allow seed emergence and even prevents infiltration

a. Porosity

b. Puddling

c. Crusting

d. Compaction

488. The pore spaces meant to drain excess moisture

a. Macropores

b. Micropores

c. Mesopores

d. Endopores

489. Movement of heat in the soil is called

a. Conduction

b. Consistence

c. Capillarity

d. Insulation

490. Bulk density is more meaningful to practical agriculture than particle density

a. Bulk density indicates the physical condition of the soil

b. Bulk density indicates the porosity and drainage condition of the soil

c. Bulk density indicates the biological condition of the soil

d. Bulk density indicates the dryness of the soil

491. This is not a soil structure

a. Crumb

b. Platy

c. Loam

d. Prismatic

492. Sticky when wet is a characteristic of

a. Loam

b. Clay

c. Silt

d. Rock

493. Grittiness is a characteristic of

a. Clay

b. Silt

c. Sand

d. Loam

494. Poorly drained condition is a characteristic of

a. Crumb structure

b. Platy structure

c. Prismatic structure

d. Single grained

495. The pH of the soil at which the soil colloids possess no net charge.

a. Neutrality

b. Alkaline

c. Acidic

d. Zero point of charge

496. Alkali soils with pH of less than 8.5 and an electrical conductivity greater than or equal to 4 mmhos/cm.

a. Alkaline

b. Saline

c. Saline-sodic

d. Sodic

497. The only group of soil organisms which can thrive at any soil pH range.

a. Actinomycetes

b. Azotobacter

c. Bacteria

d. Fungi

498. The first redox reaction to occur upon submergence of an aerated soil.

a. Disappearance of oxygen

b. Disappearance of carbon dioxide

c. Disappearance of nitrate

d. Formation of methane

499. This macronutrient is a part of the middle lamella and is deficient in acid upland soil.

a. Nitrogen

b. Potassium

c. Calcium

d. Magnesium

500. Movement of inorganic and organic materials from one horizon to another, either up or down

a. Addition

b. Removal

c. Translocation

d. Transformation

501. They are soft, unconsolidated deposits of calcium carbonate.

a. Calcium carbonate

b. Calcium oxide

c. Marl or marlstone

d. Slag

502. The major group of soil microorganisms where molds and mushrooms belong a. Algae

b. Fungi

c. Actinomycetes

d. Bacteria

503. Leaves and stems accumulate in the forest. Remnants of annual and perennial grasses are trampled in a pastureland. These illustrate how the kind and amount of organic materials decomposed can affect soil formation. Which soil formation factor is being described here? a. Climate

b. Parent material

c. Living organisms

d. Temperature

504. In soil genesis, what is considered to be the starting point of the soil formation at time zero?

a. master horizons

b. Bedrock

c. Parent material

d. magma

505. The most dominant soil microorganisms in the organic layer of forest soils.

a. Algae

b. Actinomycetes

c. Bacteria

d. Fungi

506. Soil conditions which can reduce the ferric to ferrous, hence, making the iron-phosphate complex more soluble a. Continuous tillage

b. Prolonged anaerobic conditions

c. Organic matter application

d. Liming

507. It is a wet oxidation method of determining the organic matter content of soils.

a. Combustion

b. Micro-Kjeldahl method

c. Titration

d. Walkey-Black method

508. Organic compounds which range in complexity from simple sugars and starches to cellulose.

a. Fats and waxes

b. Lignins

c. Carbohydrates

d. Proteins

509. The process by which one plant infuses the soil with a chemical that affects the growth of other plants.

a. Alleilopathy

b. Production of antibiotics

c. Productivity of hormones

d. Synergistic effects

510. If a ring without crack is formed in the roll method of determining texture; the texture is most likely

a. Sandy loam

b. Loamy sand

c. Clay

d. Clay loam

511. Which among this mineral does not contribute any soil nutrient?

a. Quartz

b. Talc

c. Apatite

d. Calcite

512. Aside from carbon and hydrogen, the other macroelement constituent of organic compound in the plant is a. Oxygen

b. Nitrogen

c. Potassium

d. Calcium

513. This horizon is seldom reached by the plant roots, and is little affected by soil forming factors because it is outside the zone of soil development.

a. C horizon b. B horizon c. A.B horizon d. B horizon

514. Involved in energy storage in the plant and is a constituent of phospholipids, nucleoproteins, and is deficient in acid upland soil.

b. Phosphorus c. Potassium

d. Calcium

515. This micronutrient is needed in nitrogen fixation by leguminous plant and is usually deficient in acid upland soil.

a. Zinc

b. Molybdenum

c. Iron

d. Manganese

516. In a very extremely acidic soil, these elements are toxic to plants except a. Aluminum

b. Calcium

c. Iron

d. Manganese

517. Which of the following elements is not essential to plant growth?

a. Nitrogen

b. Molybdenum

c. Copper

d. Aluminum

518. It is not a function of organic matter in the soil.

a. Increase C.E.C

b. Provides carbon and energy source to soil organisms

c. Provides essential nutrients

d. Provides soil air

519. The soil enzyme which catalyzes the hydrolysis of starch a. Amylase

b. Lipase

c. Cellulase

d. Catalase

520. The sum of all tillage operations, cropping practices, fertilizer, lime and other treatments conducted on, or applied to a soil for the production of plants.

a. Soil fertility

b. Soil management c. Quartz d. Calcium carbonate

553. The most resistant rock-forming mineral. a. Olivine b. Pyroxene c. Feldspar d. Quartz

554. The reaction between water and the elements of the rock or mineral. a. Hydration b. Hydrolysis c. Carbonation d. Oxidation

555. Stokes' Law states that settling of particles in a liquid medium is directly proportions to the square of its a. Weight b. Mass c. Diameter d. Density

556. The type of soil structure common in A horizons. a. Granular b. Plate like c. Block like d. Prism like

557. It is considered as the start of aggregation a. Dispersion b. Flocculation c. Cementation d. Attraction

558. A basic cation which inhibits aggregation a. calcium 2 plus b. sodium plus c. potassium plus d. magnesium 2 plus c. Calcium ion 2 plus d. Hydrogen ion plus

573. Which one of the element possesses a positive charge? a. Zn b. Cl c. No 3 d. S.O 4

574. The net charge of most agricultural soil is _ _. a. Positive b. Negative c. A and b d. Zero

575. This colloid obtains its negative charge from dissociation of H superscript plus ions from carboxylic and/or phenolic functional groups. a. Allophane b. Montmorillonite c. Humus d. Kaolinite

576. The kind of charge produced through isomorphous substitution is a. pH dependent charge b. Isomorphous charge c. Permanent charge d. Temporary charge

577. This ion aids in the dispersion of colloids a. sodium plus b. calcium two plus c. magnesium two plus d. hydrogen plus

578. This ion aids in flocculation of colloids a. sodium ion b. calcium ion 2 plus c. chloride ion d. nitrate ion c. C horizon d. E horizon

586. A horizon that has the properties of two adjacent horizons. a. Master horizon b. Diagnostic horizon c. Transition horizon d. Genetic horizon

587. The abrupt change in texture or mineralogy in the soil profile is termed a. Lithologic discontinuity b. Pedologic irregularity c. Horizonation d. None of the above

588. The rock that has been weathered but has retained the general rock structure is called a. Concretion b. Mottles c. Saprolite d. C horizon

589. It is the standard reagent to determine the cation exchange capacity of the soil. a. Ammonium acetate b. Sodium hexametaphosphate c. Ammonium phosphate d. Potassium chloride

590. A crop residue that has 75% organic carbon and 5% total nitrogen will have a C/N ratio of a. 20:1 b. 10:1 c. 15:1 d. 25:1

591. With the assumption that N is a component of O.M, to calculate the total N of the soil is to multiply O.M by: a. 2% b. 3%

c. 4%

d. 5%

592. Earthworm burrowing activity in the soil enhances a. Aeration b. Drainage c. water holding capacity d. A and B

593. Which crop is not capable of N-fixation?

a. Garden pea

b. Peanut

c. Bean

d. Potato

594. Sunlight is the specific source of energy of this microorganisms a. Autotrophs b. Chemoautotrophs c. Photoautotrophs d. Heterotrophs

d. Heterotrophs

595. A greenhouse gas that is produced by the decomposition of organic matter in wet soils such as in rice paddies. a. Carbon dioxide b. Methane c. Carbon monoxide d. Hydrogen sulfide

596. A greenhouse gas that is produced during decomposition of organic matter in well-drained soils. a. Carbon dioxide b. Methane c. Carbon monoxide d. Hydrogen sulfide

597. A 50 Kg Urea (46-0-0) contains how many kilograms of nitrogen? a. 23 b. 46 c. 2.3 d. 4.6

d. Contour hedgerow

604. A type of erosion that results from the natural processes of weathering whereby soil erosion is nearly of the same rate of soil formation?

a. Accelerated erosion

b. Rill erosion

c. Sheet erosion

d. Geologic erosion

605. An instrument that is used to locate contour lines in a sloping area.

a. Haga

b. Level hose

c. A-frame

d. Telescope

606. A type of erosion control applicable to areas undergoing negligible erosion. a. Contour farming b. Preventive type c. Terracing d. Rehabilitative type

a. Sedimentary rocks

b. Metamorphic rocks

c. Igneous rocks

d. Volcanic rocks

608. Volcanic rocks consisting of accumulation of fragments blasted from volcanoes are a. Sediments

b. Pyroclastics

609. In the Mohs' scale of hardness of minerals, it is the softest mineral. a. Quartz

b. Gypsum

c. Talc

d. Diamond

610. The clay mineral with an average cation exchange capacity of 5 to 15 me/100 g. a. Montmorillonite b. Kaolinite c. Illite d. Vermiculite

611. At high moisture content in the soil, soil water potential is a. Low b. High c. No relation d. None of the above

612. At low moisture content in the soil, soil moisture tension is a. Low b. High c. No relation d. None of the above

613. If a crop residue contains 60% organic carbon and 5% total nitrogen, its C/N ratio is a. 10:1 b. 12:1 c. 15:1 d. 20:1

614. Which of the following microorganisms is very sensitive to potassium levels in soil and therefore useful in diagnosing potassium deficiency? a. Pseudomonas denitrificans b. Aspergillus niger c. Azotobacter chroococcum d. Nitrobacter agilis

615. The most efficient organic matter decomposers under acidic soil conditions are the

a. Bacteria

b. Actinomycetes

c. Fungi

d. Protozoa

616. A soil with bulk density of 1.3 grams per cubic centimeter and particle density of 2.60 grams per cubic centimeter will have a porosity of:

a. 5%

b. 25%

c. 50%

d. 75%

617. Type of soil structure best suited for growing upland crops a. Massive

b. Platy

c. Crumb

d. Single-grain

618. A substance diagnostic horizon characterized by silicate clay accumulation. a. Argillic b. Nitric c. Spodic d. Cambic

619. A highly weathered subsurface horizon consisting of an accumulation of Fe and Al oxides. a. Argillic b. Spodic c. Cambic d. Oxic

620. A hard pan strongly cemented by silica. a. Duripan b. Calcic c. Fragipan d. Gypsic

621. The soil moisture regime characterized by sufficient moisture throughout the year. a. Aquic b. Udic c. Ustic d. Aridic

622. The soil temperature regime when the average annual temperature is more than 22 degrees Celsius and the difference between mean summer and mean winter is less than 5 degrees Celsius. a. Isothermic b. Isohyperthermic c. Isomesic d. Isofrigid

623. These are soils with little or no profile development. a. Udepts b. Fluvents c. Udands d. Ustalfs

624. These are soils formed from volcanic ash and young volcanic materials. a. Udepts b. Fluvents c. Udands d. Ustalfs

625. The cracking and swelling soils common in lowland areas which are used for rice production. a. Orthods b. Ustolls c. Ustalfs d. Uderts

626. These are well-developed soils with low base saturation common in forest and upland areas. a. Ustalfs b. Ustults c. Ustolls

d. Usterts

627. These are highly weathered soils in the humid tropics. a. Udalfs b. Udults c. Udoxs d. Ustepts

628. The name Typic Tropudults is for the category of a. Order

b. Great group

c. Subgroup

d. Suborder

629. The standard procedure to determine nitrogen content of soils.

a. Potentiometric method

b. Kjeldahl method

c. Walkey-Black method

d. X-ray diffraction method

630. A group of soils having the same profile characteristics and parent materials a. Soil type b. Soil series c. Soil association d. Soil phase

631. A type of soil survey which procedure 1:15,000 to 1:5,000. a. Exploratory b. Reconnaissance c. Semi-detailed d. Detailed 632. Maahas clay is an example of a a. Soil type b. Soil series c. Soil association d. Soil phase

633. The most important cause of soil degradation. a. Soil pollution b. Soil erosion c. Soil denudation d. All of the above

634. The first step of soil erosion by water. a. Detachment b. Transportation c. Deposition d. Rainfall impact

635. A type of soil erosion characterized by uniform removal of soil. a. Rill erosion b. Gully erosion c. Sheet erosion d. Surface erosion

636. The ability of rainfall to cause soil erosion. a. Erodibility b. Erosivity c. Detachability d. None of the above

637. It is not a master horizon a. O b. A c. B d. R

638. It refers to the true soil. a. Solum b. Regolith c. Soil profile d. B horizon

639. A type of B horizon showing significantly clay accumulation. a. Bw b. Bt c. Bk d. Bc

640. The pores created by soil animals are called a. Capillary pores b. Biopores c. Voids d. None of the above

641. It is used to destroy organic matter during the textural analysis.

a. Calgon

b. H 2 O 2

c. H.C.l

d. H 2 S O 4

It is the chemical dispersing agent duri a. Sodium phosphate b. Sodium hexametaphosphate c. Calcium phosphate d. Calcium chloride

643. A diagnostic horizon showing strong human influence such as phosphorus accumulation. a. Umbric b. Melanic c. Historic d. Anthropic

644. A diagnostic horizon that is like argillic except for its high sodium content. a. Spodic b. Natric c. Cambic d. Salic

645. The soil moisture regime that is characterized by water saturation a. Udic b. Aquic c. Ustic d. Xeric

646. The soil order of organic soils. a. Histosols b. Entisols c. Andisols d. Mollisols

647. They are young volcanic soils which are fertile except for their high P fixing capacity.

b. Andisols

648. They are swelling and cracking soils common in lowlands. a. Entisols b. Andisols c. Alfisols d. Vertisols

649. The clay mineral characterized by a basal spacing of 7 Angstrom. a. Illite b. Kaolinite c. Montmorillonite d. Allophane

650. The clay mineral characterized by a basal spacing of 10 Angstrom. a. Illite b. Kaolinite c. Montmorillonite d. Chlorite

51. The oven-drying of soil samples is normally done at this temperature a. 70 degrees Celsius b. 105 degrees Celsius c. 205 degrees Celsius d. 550 degrees Celsius

d. 550 degrees Celsius a. Capillary water

b. saturated water

c. Gravitational water

d. Percolating water

653. The moisture content of the soil at which plants wilt and fail to recover their turgidity when placed in a dark humid atmosphere.

a. Field capacity

b. Permanent wilting point

c. Hygroscopic coefficient

d. None of the above

654. The amount of moisture in a dry soil.

a. Hygroscopic coefficient

b. Adsorbed water

c. Gravitational water

d. Field capacity

655. The most active agent of soil erosion process in the Philippines and other areas in the humid tropics

a. Wind

b. Ice

c. Water

d. Glaciers

656. The wise use of land especially with respect to soil erosion control

a. sustainable agriculture

b. soil capability

c. soil conservation

d. soil management

657. The process by which soil nutrients are washed down by water from the root zone of the plants

a. crop removal

b. leaching

c. volatilization

d. denitrification

658. Growing of several crop species on a piece of land in spatial arrangement a. Monocropping b. Intercropping c. Alley cropping d. Multiple cropping

659. Biological control of soil erosion a. Contouring b. Rockwalling c. Strip cropping d. Terracing

660. Mechanical method of controlling soil erosion a. Terracing b. Mulching c. Strip cropping d. Alley cropping

661. This type of structure has disc-like aggregates and can be found in newly opened lands a. columnar b. massive c. crumb d. platy

662. Highly weathered soils with B horizon consisting primarily of sesquioxides a. Oxisol b. Alfisol c. Vertisol d. Aridisol

663. Order of montmorillonitic soils that forms crack during drying a. Spodosol b. Vertisol c. Histosol d. Oxisol

664. A diagnostic horizon with an accumulation of free iron oxides and organic matter

a. Spodic

b. Cambic

c. Oxic

d. Nitric

665. Net Nitrogen immobilization in the soil occurs if the C/N is

a. less than 20:1

b. greater then 20:1

c. greater than 35:1

d. less than 15:1

666. Individually, which among the following soil microorganisms have the least biomass?

a. Actinomycetes

b. Fungi

c. Bacteria

d. Protozoa

667. Which of the following soil organisms are acid-loving?

a. Fungi

b. Protozoa

c. Bacteria

d. Actinomycetes

668. The following illustrates how the value of B. D. is higher in the underlying subsoil, except one

a. there is compaction brought about by the weight of overlying horizons

b. there is less root penetration in subsoil

c. subsoil is well-aggregated

d. O.M content is lower in subsoil

669. It states that the yield of the plant is regulated by the nutrient present in the lowest amount relative to its optimum requirement.

a. Stoke's law

b. Mineral theory

c. Humus theory d. Law of minimum

670. Which among the following is not true for humus?

a. unstable and can be further degraded

b. representative of organic colloids

c. a complex organic product

d. high molecular weight

671. Which is not a characteristic of cation exchange reactions?

a. Instantaneous

b. Reversible

c. Stoichiometric

d. Specific

672. Which is not a characteristic of upland soils?

a. Upland soils are aerobic most of the time.

b. Organic matter decomposes with C-O 2 as a major product

c. Nutrient elements exist generally in their oxidized state

d. Nutrient elements exist generally in their reduced state

673. Which is not a characteristic of lowland soils?

a. Lowland soils are anaerobic most of the time.

b. Organic matter decomposes with methane, hydrogen sulfide, organic acids, alcohols and ketones as products

c. Nutrient elements exist generally in their oxidized state

d. Nutrient elements exist generally in their reduced state

674. Type of chemical weathering that takes place within the soil solum

a. Geochemical weathering

b. Pedochemical weathering

c. Oxidation

d. Reduction

675. The attack of the mineral by water is termed _ _.

a. Hydrolysis

b. Hydration

c. Oxidation

d. Reduction

676. Equilibrium reaction between a metal ion and a complexing agent characterized by bond formation between the metal and complexing agent.

a. Oxidation

b. Reduction

c. Chelation

d. Hydration

677. Which of the following statement is not true regarding stability and weathering of minerals:

a. Stability of mineral generally increases with increasing linkage between tetrahedral

b. Stability within structural group increases with increased isomorphous substitution.

c. Stability within a structural group decreases with decreasing electronegativity of metal ions

d. Stability is influenced by the type and structure of metal ion-oxygen polyhedral linking silicate units

678. Describes the order in which minerals crystallize from magma:

a. Bowen's reaction series

b. Lyotropic series

c. Discontinuous series

d. Continuous series

679. It describes the formation of the mafic minerals (olivine, pyroxene, amphibole and biotite) each taking turns to form as the temperature progressively decreases:

a. Discontinuous reaction series

b. Continuous reaction series

c. Lyotropic series

d. Bowen's reaction series

680. It describes the evolution of the plagioclase feldspars as they evolve from being calcium rich to more sodium rich.

a. Discontinuous reaction series

b. Continuous reaction series

c. Lyotropic series d. Bowen's reaction series

681. Which among the following is considered as variable charge clay?

a. Kaolinite

b. Vermiculite

c. Montmorillonite

d. Intergrades

682. Calculate the weight (g) of calcium ion 2 plus needed to replace 1 g of hydrogen ion plus.

a. 20

b. 10

c. 15

d. 50

683. Calculate the weight (g) of calcium ion 2 plus needed to replace 1 g of ammonium ion 4 plus.

a. 2.22

b. 1.11

c. 3.33

d. 4.44

684. The net accumulation of materials at the interface between a solid phase and an aqueous solution phase is called a. Adsorption

b. Absorption

c. Attraction

d. Adhesion

685. A soil has a pH of 5.5 and a C.E.C of 20 me/100g. The grower needs to lime the soil to pH 6.5. If the %B.S at pH 5.5 is 50%, and 75% at pH 6.5, calculate the amount of CaCO 3 required to raise the pH of 1 hectare of soil.

a. 10 tons calcium carbonate per hectare

b. 50 tons calcium carbonate per hectare

c. 30 tons calcium carbonate per hectare

d. 5 tons calcium carbonate per hectare

686. It is a measure of salinity or concentration of dissolved salts a. Electrical conductivity

b. Soil pH c. Total dissolved solids

d. Residual calcium carbonate value

687. A property of solutions and has been used to quantify the alkalinity hazards of irrigation water applied to soils:

a. Electrical conductivity

b. Soil pH

c. Total dissolved solids

d. Residual calcium carbonate value

688. Refers to total concentration of inorganic solids and is usually expressed in mgL ^{-1} or ppm.

a. Electrical conductivity

b. Soil pH

c. Total dissolved solids

d. Residual calcium carbonate value

689. System classification approach that attempts to organize the divisions of soils from a more holistic appraisal of soil attributes.

a. Natural

b. Technical

c. Broad

d. Narrow

690. Pesticides will be retained much longer in soils with a. Low organic matter

b. High moisture content

c. 2:1 dominant clay type

d. Low pH

691. Once a soil has been placed under cultivation, its organic matter content usually a. Increases

b. Decreases

c. Relatively unchanged

d. Unchanged

692. Tissue nutrient analysis is used to determine the nutrient status of the plants. Correct sampling of tissue always gives reliable results. The most common tissue used is a. Leaf

b. Petiole

c. Bark

d. Roots

693. One important practical application of soil survey is to match it with the basic requirements of production systems. This is referred to as:

a. Soil survey and classification b. Suitability assessment c. Soil analysis d. Soil morphological description

694. San Manuel loam can be cultivated safely and extensively to most crops. This soil type belongs to what suitability class? a. Class A b. Class B c. Class C d. Class D

695. A soil condition usually associated with a salinity problem is a. fine texture b. poor internal drainage c. level topography d. soil acidity

696. The fertilizer grade 10-12-10 means:

a. 10% N - 12% P - 10% K

b. 10 kilograms N -12 kilograms P -10 kilograms K

c. 10 percent N minus 12 percent P 2 O 5 minus 10 percent K 2 O

d. 10 kilograms N - 12 kilograms P 2 O 5 - 10 kilograms K 2 O

697. A 500 Kg Urea (46-0-0) contains how many kilograms of nitrogen? a. 230 b. 460 c. 23 d. 46

698. It is a characteristic of rainfall that falls per unit time usually expressed in millimeter per hour

a. Drop size

b. Amount

c. Intensity

d. Distribution

699. Soil colloids with the lowest cation exchange capacity.

a. Allophane

b. Montmorillonite

c. Organic matter

d. Kaolinite

700. Which among the following has the highest N and P contents?

a. poultry manure

b. cattle manure

c. goat manure

d. guano

701. Iron deficiency is commonly observed in these types of soils:

a. acid soils

b. neutral soils

c. alkaline soils

d. saline soils

02. Iron toxicity is commonly observed in this type of soils.

a. acid soils

b. neutral soils

c. alkaline soils

d. saline soils

703. Organic materials with wide C/N ratios are not ready sources of available nitrogen because the nitrogen that they contain is subject to a. Nitrification

b. Volatilization

c. Immobilization

d. Fixation

704. The soil microbial population is generally highest in the a. A horizon

b. B horizon

c. C horizon

d. B.2 horizon

705. Chemoautotrophs are those organisms which derive their energy from

a. Sunlight

b. Oxidation of organic materials

c. Fermentation

d. Oxidation of inorganic substances

a. Size of the individuals

b. Number of the individuals

c. Form of the individuals

d. Size and number of the individuals

b. Moisture

c. Oxygen supply

d. All of the above

708. A type of microscope which provides 3-dimensional view of the soil microorganisms is called a. Light microscope b. Scanning electron microscope c. Transmission electron microscope d. Immune-fluorescent microscope

709. A 1:1000 soil-water dilution means that one part of soil is suspended in a. 9 parts of sterile water

b. 99 parts of sterile water

c. 999 parts of sterile water

d. 1000 parts of sterile water

710. In a legume biological nitrogen fixing system, the microsymbiont is a. Bacteria

b. Actinomycetes

c. Algae

d. Fungi

711. C-O 2 evolution in soil is a function of a. Microbial population

b. Aeration

c. pH

d. All of the above

712. The amount of molecular nitrogen ( N 2 ) in the atmosphere is about a. 88%

b. 78%

c. 68%

d. 58%

713. Minimum slope criteria which is considered vulnerable to soil erosion a. 10%

b. 12%

c. 18%

714. It is the systematic examination, description, classification, and mapping of the soils in a given area a. Soil survey

b. Soil science

c. Soil classification

d. Soil physics

715. A type of soil survey where the size of mapping unit is 0.5 to 4 hectares.

a. Intensive survey

b. Reconnaissance survey

c. Semi-detailed survey

d. Detailed survey

716. The total number of soil orders classified under the Soil Taxonomy a. 9

b. 11

c. 10

d. 12

717. A subsurface horizon with silicate accumulation accompanied by more than 15% exchangeable sodium a. Nitric b. Oxic c. Kandic d. Spedic

d. Spodic

718. A surface layer that is dark-colored, with more than 1 percent organic matter and typically friable granular structure. a. Mollic epipedon b. Umbic epipedon c. Ochric epipedon d. Melanic epipedon

719. A man-made surface horizon which was produced by long-continued manuring and contains artifacts such as bits of bricks and pottery through its depth. a. Anthropic epipedon b. Histicepipedon c. Plaggenepipedon d. Umbricepipedon

720. A subsurface horizon which is typically indicated by the accumulation of clay a. Argillic horizon b. Agric horizon c. Cambic horizon d. Oxic horizon

721. The property of the soil that enables water, or roots to move through it a. Infiltration b. Density c. Permeability d. Percolation

722. A soil temperature regime wherein the mean annual soil temperature is 22 degrees Celsius or higher and the difference between mean summer and mean winter temperature is less than 5 degrees Celsius.

a. Mesic

b. Thermic

c. Hyperthermic

d. Isohyperthermic

723. Increased bulk density is not favorable in practical agriculture. Which of the following may lead to reduced bulk density?

a. Less aggregation and root penetration

b. Compaction caused by the weight of the overlying layers

c. Addition of organic matter in large amounts

d. Heavy foot traffic

724. The following can be used as contour hedges except one

a. camachile

b. ipil-ipil

c. eggplant

d. kakawate

725. A relatively new term for an old practice of planting agricultural crops along with or in sequence with woody perennial. This can provide a better source of income for the community.

a. multicropping

b. Agroforestry

c. multistorey cropping

d. Upland farming

Write True if the statement is correct, otherwise write False

726. Field capacity is an estimate of the upper limit of available moisture range.

727. Infiltration is the downward entry of water via the soil surface.

728. Permanent wilting point is the lower limit of the available moisture range.

729. The higher the soil moisture tension, the greater the amount of water stored or retained in the soil.

730. Capillarity is the ability of a liquid to flow against gravity.

731. Soil colloids are greater than 0.0001 millimeters in size.

732. Illite is a 2:1 expanding type silicate clay.

733. The C.E.C of soils decreases with increasing amount of clay and organic matter.

734. C.E.C can be expressed in me/100g soil or cmolc/kg soil.

735. Soils generally possess a net positive charge.

736. Aluminum is the central ion in the tetrahedral units of clay colloids.

_737. Unit layers of kaolinite are held together tightly by H-bonding.

738. Soils high in montmorillonite do not swell nor shrink on wetting and drying.

739. Soils dominated by kaolinite are good bases for roadbeds and building foundations.

740. Chlorite is a 2:1:1 non expanding type silicate clay.

741. Clayey soils generally have higher C.E.C than a sandy soil.

742. Negatively charged colloids attract cations from soil solution which become absorbed on the surface.

743. Low C.E.C corresponds to low nutrient retention capacity.

744. Sodium rich soils are in dispersed state.

745. The concentration of hydrogen ions increases as pH increases.

746. The pH range 6.6 to 7.3 is considered neutral.

747. Main objective of soil sampling is to collect a small amount of soil sample weighing about 0.5 kilograms that will represent the soil in a large area.

748. Soil samples should be collected from the surface layer (20 to 30 centimeters) for shallow rooted crops.

749. Olsen method is use for determination of available P of neutral or alkaline soils.

750. Moisture release curve is a graph showing the relationship between moisture content and moisture tension of the soil and the characteristic of soil itself.

G.E

Table summary: A list of 200 numbered entries, each associated with a letter grade of A, B, C, or D. The data is distributed across the entries without a single dominant grade, featuring a mix of values such as entry 1 being B, entry 50 being C, entry 100 being B, and entry 200 being C.

Table summary: A mapping of numeric IDs from 201 to 400 to categorical values A, B, C, and D. The data is organized in six pairs of columns, with IDs increasing sequentially. For example, ID 201 is A, 204 is B, 206 is C, and 209 is D. The values are distributed across the entire range, with ID 400 ending on value C.

Table summary: An answer key for items 401 through 600, organized in columns. For example, item 401 is B, 451 is C, 501 is C, 551 is D, and 600 is A.

Table summary: A list of answers and true false values for items numbered 601 through 750. The data is organized in columns of item numbers and their corresponding values. For example, item 601 is C, 602 is D, and 726 is TRUE, while 729 and 731 are FALSE.

1. Keys to Soil Taxonomy 12 superscript th ed. 2014 United States of America Department of Agriculture (U.S.D.A) Natural Resources Conservation Service by Soil Survey Staff U.S.A, 2014

References

2. World Reference Base for Soil Resources 2014

International Soil Classification System for Naming Soils and Creating Legends for Soil Maps Food and Agriculture Organization (F.A.O) of the United Nations Rome, 2014

3. The Soil Survey Manual Technical Publication No. 2 Bureau of Soils and Water Management (B.S.W.M) by The Soil Survey Division Staff; Integrated Soil Resources Information Service Staff Diliman, Quezon City, December 2008

4. Primer on Soil Science Wilfredo C. Cosico, Ph.D. Agricultural Systems Cluster College of Agriculture, Up Los Baños Laguna, 2004

5. Organic Fertilizers: Their Nature, Properties and Use

5. Wilfreu Soils and Agro. Agricultural Systems College of Agriculture, Up Los Angeles Laguna, 2010

6. Soil Science 1 Laboratory Manual

Soils and Agro-Ecosystems Division Agricultural Systems Cluster College of Agriculture, Up Los Baños Laguna, Revised 2014

7. Basic Soil Fertility Roberto Nartea College of Agriculture, Up Los Baños Laguna

8. Principles of Soil Chemistry Kim H. Tan 12 superscript th ed University of Georgia C.R.C Press Athens, Georgia, 2011

9. Philippine Soils: Their Distribution, General Land-use, and Parent Materials Nicanor C. Fernandez and Jose I. Clar de Jesus Department of Soil Science Up Los Baños, 1980

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