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SOIL AND SOIL AND SOILCONCEPTS SOILCONCEPTS

BYBYALLAH DAD KHANALLAH DAD KHAN

(Fourth Presentation)(Fourth Presentation)

Soil Definition (SSCA) Soil Definition (SSCA)

(i) (i) The unconsolidated mineral or organic material on the immediate The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth surface of the Earth that serves as a natural medium for the growth of land plants. of land plants.

ii) The unconsolidated mineral or organic matter on the surface of ii) The unconsolidated mineral or organic matter on the surface of the Earth that has been subjected to and shows effects of genetic the Earth that has been subjected to and shows effects of genetic and environmental factors of: climate (including water and and environmental factors of: climate (including water and temperature effects), and macro- and microorganisms, conditioned temperature effects), and macro- and microorganisms, conditioned by relief, acting on parent material over a period of time.by relief, acting on parent material over a period of time.

Source ( Soil Science Society of AmericaSource ( Soil Science Society of America  

Soil Definition(STSE)Soil Definition(STSE)

Soil is a natural body comprised of solids (minerals and organic Soil is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occurs on the land surface, occupies matter), liquid, and gases that occurs on the land surface, occupies space, and is characterized by one or both of the following: space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural energy and matter or the ability to support rooted plants in a natural environment.environment.

Source (Soil Taxonomy, second edition)Source (Soil Taxonomy, second edition)

Soil Geological DefinitionSoil Geological Definition

Loose surface of the earth as distinguished from solid bedrock; Loose surface of the earth as distinguished from solid bedrock; support of plant life not required.support of plant life not required.

Soil Traditional Definition Soil Traditional Definition

Material which nourishes and supports growing plants; includes Material which nourishes and supports growing plants; includes rocks, water, snow, air.rocks, water, snow, air.

Soil Definition by Component Soil Definition by Component

Mixture of mineral matter, organic matter, water, and air.Mixture of mineral matter, organic matter, water, and air. Component definition: Mixture of mineral matter, organic matter, Component definition: Mixture of mineral matter, organic matter,

water, and air.water, and air.

Soil Taxonomy Definition Soil Taxonomy Definition

Collection of natural bodies of the earth’s surface, in places modified Collection of natural bodies of the earth’s surface, in places modified or even made by man or earthy materials, containing living matter or even made by man or earthy materials, containing living matter

and supporting or capable of supporting plants out of doors.and supporting or capable of supporting plants out of doors. Its upper limit is air or shallow water and its lower limit is the depth Its upper limit is air or shallow water and its lower limit is the depth to which soil weathering has been effective.to which soil weathering has been effective.

Soil Health and Ecosystem Soil Health and Ecosystem Soil health is an assessment of ability of a soil to meet its range of Soil health is an assessment of ability of a soil to meet its range of

ecosystem functions as appropriate to its environment. Also refers ecosystem functions as appropriate to its environment. Also refers to the condition of the soil, including its ecosystems (minerals, to the condition of the soil, including its ecosystems (minerals, nutrients, and microbial activity), pH, and structure. The Soil nutrients, and microbial activity), pH, and structure. The Soil Science Society defines soil health as the capacity of a specific kind Science Society defines soil health as the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitationand air quality, and support human health and habitation

Soil Health and Ecosystem contd Soil Health and Ecosystem contd Ecosystems that benefit humans. Collectively, these benefits are Ecosystems that benefit humans. Collectively, these benefits are

known as ecosystem services and include products like clean known as ecosystem services and include products like clean drinking water and processes such as the decomposition of wastes. drinking water and processes such as the decomposition of wastes. Ecosystem services have been grouped into four broad categories: Ecosystem services have been grouped into four broad categories: provisioning, such as the production of food and availability of water; provisioning, such as the production of food and availability of water; regulating, such as the control of climate and diseases; supporting, regulating, such as the control of climate and diseases; supporting, such as nutrient cycles and crop pollination; and cultural or social, such as nutrient cycles and crop pollination; and cultural or social, such as norms, ideas, and spiritual and recreational benefits.such as norms, ideas, and spiritual and recreational benefits.

Oganic MatterOganic Matter

Classified into two major groups composing a humic and non-humic Classified into two major groups composing a humic and non-humic substances. Soil organic matter is thermodynamically unstable and substances. Soil organic matter is thermodynamically unstable and is part of the natural balance between production, decomposition, is part of the natural balance between production, decomposition, transformation, and resynthesis of various organic substances. The transformation, and resynthesis of various organic substances. The humified fraction is composed of humic, fulvic, and humin and is the humified fraction is composed of humic, fulvic, and humin and is the most stable. The non-humic portion is the relatively unstable and most stable. The non-humic portion is the relatively unstable and most labile fraction and is most easily decomposed.most labile fraction and is most easily decomposed.

Soil Organic Carbon: Is related directly to soil organic matter. Soil Soil Organic Carbon: Is related directly to soil organic matter. Soil organic matter consists of 50 to 58 percent soil organic carbon. A organic matter consists of 50 to 58 percent soil organic carbon. A simple unit of 1.724 is used to convert total carbon into soil organic simple unit of 1.724 is used to convert total carbon into soil organic mattermatter

Soil As a portion of the landscapeSoil As a portion of the landscape

Collection of natural bodies occupying portions of the earth’s Collection of natural bodies occupying portions of the earth’s surface that support plants and that have properties due to the surface that support plants and that have properties due to the integrated effect of climate and living matter, acting upon parent integrated effect of climate and living matter, acting upon parent material, as conditioned by relief, over periods of time.material, as conditioned by relief, over periods of time.

Soil Forming ProcessesSoil Forming Processes

TranslocationsTranslocations

TransformationsTransformations

AdditionsAdditions

LossesLosses

1.Translocation 1.Translocation

Translocation refers to the physical movement of material within Translocation refers to the physical movement of material within soil. The material can be in the solid, liquid or gaseous form, the soil. The material can be in the solid, liquid or gaseous form, the movement can be in any direction from and to any horizon. For movement can be in any direction from and to any horizon. For instance clay, organic matter and iron and aluminum hydrous oxides instance clay, organic matter and iron and aluminum hydrous oxides are commonly moved from the surface horizon to a subsurface are commonly moved from the surface horizon to a subsurface horizon. Conversely, in very dry climates salts are moved upwards horizon. Conversely, in very dry climates salts are moved upwards in solution by capillarity, and in very cold climates solid mineral in solution by capillarity, and in very cold climates solid mineral fragments are moved upwards by frost action.fragments are moved upwards by frost action.

2.Transformation2.Transformation

The chemical weathering of sand and formation of clay minerals, The chemical weathering of sand and formation of clay minerals, transformation of coarse OM into decay resistant organic transformation of coarse OM into decay resistant organic compoundscompounds

3.Addition3.Addition

Materials added to the soil, such as decomposing Materials added to the soil, such as decomposing vegetation and organisms (organic matter--OM), or new vegetation and organisms (organic matter--OM), or new mineral materials deposited by wind or water.mineral materials deposited by wind or water.

4.Losses4.Losses

Through the movement of wind or water, or uptake by plants, soil Through the movement of wind or water, or uptake by plants, soil particles (sand, silt, clay, and OM) or chemical compounds can be particles (sand, silt, clay, and OM) or chemical compounds can be eroded, leached, or harvested from the soil, altering the chemical eroded, leached, or harvested from the soil, altering the chemical and physical makeup of the soil.and physical makeup of the soil.

Losses occur both from the surface and from the deep subsoil. For Losses occur both from the surface and from the deep subsoil. For instance, water is lost by evapotranspiration and carbon dioxide by instance, water is lost by evapotranspiration and carbon dioxide by diffusion at the surface and, on a more catastrophic level, large diffusion at the surface and, on a more catastrophic level, large masses of soil can be stripped by erosion. Materials suspended or masses of soil can be stripped by erosion. Materials suspended or dissolved in water are the main forms of losses from the subsoil. dissolved in water are the main forms of losses from the subsoil.

Factors of Soil Formation Factors of Soil Formation

The 5 factors of soil formation are:The 5 factors of soil formation are: Parent material Climate Biota Time Topography

Parent Material Parent Material

The parent material may be mineral rock and/or organic matter. The parent material may be mineral rock and/or organic matter. When parent rock material is exposed to the atmosphere or when When parent rock material is exposed to the atmosphere or when organic matter and/or minerals are deposited on the earth’s surface, organic matter and/or minerals are deposited on the earth’s surface, soil formation begins. The type of parent material and how the soil is soil formation begins. The type of parent material and how the soil is formed will greatly influence the properties of the soil.formed will greatly influence the properties of the soil.

There are two general rules that we may state about the influence of There are two general rules that we may state about the influence of parent material on soil formation:parent material on soil formation:

Finely textured parent materials tend to weather into finely textured Finely textured parent materials tend to weather into finely textured soils. Coarsely textured parent materials tend to weather into soils. Coarsely textured parent materials tend to weather into coarsely textured soils.coarsely textured soils.

Darker minerals tend to yield more fertile soils.Darker minerals tend to yield more fertile soils.

ClimateClimate

The effect of climate on soil formation cannot be underestimated. The effect of climate on soil formation cannot be underestimated. Climate is a fundamental force of weathering that interacts with all Climate is a fundamental force of weathering that interacts with all other soil formation factors. The primary forces of climate are other soil formation factors. The primary forces of climate are precipitation and temperature. While nutrients can be released from precipitation and temperature. While nutrients can be released from primary minerals during weathering, high levels of precipitation and primary minerals during weathering, high levels of precipitation and temperature can remove, or leach, nutrients from the soil and temperature can remove, or leach, nutrients from the soil and reduce its fertilityreduce its fertility

Biota Biota

Biota is the vegetation that covers the soil, the animals that live Biota is the vegetation that covers the soil, the animals that live upon the soil, and the soil microorganisms that inhabit the soil. Soils upon the soil, and the soil microorganisms that inhabit the soil. Soils that develop in grasslands will be remarkably different than soils that that develop in grasslands will be remarkably different than soils that develop in forests. This soil formation factor is intimately influenced develop in forests. This soil formation factor is intimately influenced

by climate and changes over timeby climate and changes over time..

TimeTime

The soil profile is continually changing and developing with time. In the The soil profile is continually changing and developing with time. In the beginning, pioneer species, such as mosses and lichens, colonize rocks beginning, pioneer species, such as mosses and lichens, colonize rocks and secrete acids that weather the rocks. Microorganisms, such as bacteria and secrete acids that weather the rocks. Microorganisms, such as bacteria and fungi, are instrumental in forming soil through the decomposing organic and fungi, are instrumental in forming soil through the decomposing organic matter and binding of soil particles. Earthworms create channels, as well as matter and binding of soil particles. Earthworms create channels, as well as secrete substrates that bind soil particles together. Animals, as well as secrete substrates that bind soil particles together. Animals, as well as humans, directly and indirectly transform the soil through their many humans, directly and indirectly transform the soil through their many activities, in both positive and negative ways. Additionally, with time, the activities, in both positive and negative ways. Additionally, with time, the climate promotes changes along the earth surface and profile development.climate promotes changes along the earth surface and profile development.

Topography Topography

Topography has a direct impact on water drainage. We may Topography has a direct impact on water drainage. We may observe the effect of topography by describing a typical mountain observe the effect of topography by describing a typical mountain slope. Residual soils that form along the uplands tend to experience slope. Residual soils that form along the uplands tend to experience good drainage. The colluvium soils that form along steep slopes will good drainage. The colluvium soils that form along steep slopes will usually have excessive drainage. Finally, alluvial soils that form in usually have excessive drainage. Finally, alluvial soils that form in

the flood plains have poorer drainagethe flood plains have poorer drainage..

Soil ComponentSoil Component

Soils are multiphase systems, composed of a mixture of numerous Soils are multiphase systems, composed of a mixture of numerous kinds and sizes of mineral grains, organic fragments, air and water. kinds and sizes of mineral grains, organic fragments, air and water. The proportions of these components vary from point to point on the The proportions of these components vary from point to point on the surface of the earth, and from time to time, depending upon the surface of the earth, and from time to time, depending upon the factors of soil formation and the influence of man's activity.factors of soil formation and the influence of man's activity.

Soil Components (volume basis)

Soil Mineral Portion Soil Mineral Portion Particle size of the mineral fraction varies widely, from stones (over Particle size of the mineral fraction varies widely, from stones (over

250 mm in diameter), through cobbles (250-75 mm), gravel (75-2 250 mm in diameter), through cobbles (250-75 mm), gravel (75-2 mm), sand (2-0.05 mm), silt (0.05-0.002 mm) to clay (less than mm), sand (2-0.05 mm), silt (0.05-0.002 mm) to clay (less than 0.002 mm).0.002 mm).

Soil Organic PortionSoil Organic Portion

The The organic portionorganic portion of soils results from the accumulation of animal and  of soils results from the accumulation of animal and plant residues added to the mineral soil. It is this organic portion that plant residues added to the mineral soil. It is this organic portion that differentiates soil from geological material occurring below the earth's differentiates soil from geological material occurring below the earth's surface which otherwise may have many of the properties of a soil. Organic surface which otherwise may have many of the properties of a soil. Organic compounds undergo decomposition by soil flora and fauna. This process compounds undergo decomposition by soil flora and fauna. This process produces humus, the most active and important form of organic matter for produces humus, the most active and important form of organic matter for crop growth and soil formationcrop growth and soil formation

Role of soil organic matter in crop Role of soil organic matter in crop productivityproductivity

a. Cation exchange capacityb. Nutrient retention and releasec. Soil structure and bulk densityc. Soil structure and bulk densityd. Water-holding and snow/drain catchmentd. Water-holding and snow/drain catchmente. Biological activitye. Biological activity

Matson et al. factors affecting soil C loss from Matson et al. factors affecting soil C loss from agricultural soils includeagricultural soils include

1.1. Climate and soil typeClimate and soil type

2.2. Tillage intensity and depthTillage intensity and depth

3.3. Crop rotation decisionsCrop rotation decisions

4.4. Amount of organic inputsAmount of organic inputs

5.5. Amount of plant residue on the soil surfaceAmount of plant residue on the soil surface

6.6. Quality of plant residues returned to the soilQuality of plant residues returned to the soil

7.7. Soil biological activitySoil biological activity

8.8. Length and time of fallowLength and time of fallow

9.9. ErosionErosion

Soil Water Soil Water

The importance of The importance of soil watersoil water lies in its roles in plant growth and in  lies in its roles in plant growth and in the chemical and physical reactions that occur in soils. Water the chemical and physical reactions that occur in soils. Water provides the medium by which plants take up their nutrients in provides the medium by which plants take up their nutrients in solution through their root systems; it may also be considered a solution through their root systems; it may also be considered a plant nutrient itself. Thus water is crucial to plant growthplant nutrient itself. Thus water is crucial to plant growth

Soil Air Soil Air

Soil airSoil air plays an important role in plant growth and the activity of soil  plays an important role in plant growth and the activity of soil organisms. Its main constituents, as in the atmosphere, are organisms. Its main constituents, as in the atmosphere, are nitrogen, oxygen and carbon dioxide. Various organisms use the nitrogen, oxygen and carbon dioxide. Various organisms use the oxygen and give off carbon dioxide. The supply of oxygen has to be oxygen and give off carbon dioxide. The supply of oxygen has to be constantly replenished and this is the importance of adequate pore constantly replenished and this is the importance of adequate pore spaces or aeration within the soil. For adequate aeration spaces or aeration within the soil. For adequate aeration approximately 10% by volume of the soil should be occupied by air.approximately 10% by volume of the soil should be occupied by air.

Characteristics of High Quality SoilCharacteristics of High Quality Soil

Good soil tilthGood soil tilth Sufficient depthSufficient depth Sufficient, but not excessive, nutrient supplySufficient, but not excessive, nutrient supply Small population of plant pathogens and insect pestsSmall population of plant pathogens and insect pests Good soil drainageGood soil drainage Large population of beneficial organismsLarge population of beneficial organisms Low weed pressureLow weed pressure No chemicals or toxins that may harm the cropNo chemicals or toxins that may harm the crop Resilience to degradation and unfavorable conditionsResilience to degradation and unfavorable conditions

Soil Fertility and Conservation Soil Fertility and Conservation

Soil fertility—the ability to support plant growth—depends on various Soil fertility—the ability to support plant growth—depends on various factors, including the soil's structure or texture; its chemical composition, factors, including the soil's structure or texture; its chemical composition, esp. its content of plant nutrients; its supply of water; and its temperature. esp. its content of plant nutrients; its supply of water; and its temperature. Agriculture necessarily lowers soil fertility by removing soil nutrients Agriculture necessarily lowers soil fertility by removing soil nutrients incorporated in the harvested crops. Cultivation, especially with heavy incorporated in the harvested crops. Cultivation, especially with heavy machinery, can degrade soil structure. Agricultural soils are also vulnerable machinery, can degrade soil structure. Agricultural soils are also vulnerable to mismanagement. Exposure of soils to wind and rain during cultivation to mismanagement. Exposure of soils to wind and rain during cultivation encourages erosion of the fertile surface. Excessive cropping or grazing can encourages erosion of the fertile surface. Excessive cropping or grazing can depress soil-nutrient levels and degrade soil structure.depress soil-nutrient levels and degrade soil structure.

Soil Fertility and Conservation contdSoil Fertility and Conservation contd

Soil conservation techniques have been developed to address the range of Soil conservation techniques have been developed to address the range of soil management issues. Various methods of cultivation conserve soil soil management issues. Various methods of cultivation conserve soil fertility (see cover crop; rotation of crops). Minimum-tillage systems, often fertility (see cover crop; rotation of crops). Minimum-tillage systems, often entailing herbicide use, avoid erosion and maintain soil structure. Soil entailing herbicide use, avoid erosion and maintain soil structure. Soil fertility and agricultural productivity can also be improved, restored, and fertility and agricultural productivity can also be improved, restored, and maintained by the correct use of fertilizer, either organic, such as manure, or maintained by the correct use of fertilizer, either organic, such as manure, or inorganic, and other soil amendments. Organic matter can be added to inorganic, and other soil amendments. Organic matter can be added to improve soil structure. Soil acidity can be decreased by addition of calcium improve soil structure. Soil acidity can be decreased by addition of calcium carbonate or increased by addition of sulfuric acid.carbonate or increased by addition of sulfuric acid.

Soil and Nutrients Soil and Nutrients

Compounds of silicon, aluminum, iron, oxygen, and, in smaller quantities, calcium, Compounds of silicon, aluminum, iron, oxygen, and, in smaller quantities, calcium, magnesium, sodium, and potassium. Factors determining the nature of soil are magnesium, sodium, and potassium. Factors determining the nature of soil are vegetation type, climate, and parent rock material; geographic relief and the vegetation type, climate, and parent rock material; geographic relief and the geological age of the developing soil are also factors. Acidic soils occur in humid geological age of the developing soil are also factors. Acidic soils occur in humid regions because alkaline minerals are leached downward: alkaline soils occur in dry regions because alkaline minerals are leached downward: alkaline soils occur in dry regions because alkaline salts remain concentrated near the surface. Geologically regions because alkaline salts remain concentrated near the surface. Geologically young soils resemble their parent material more than older soils, which have been young soils resemble their parent material more than older soils, which have been altered over time by climate and vegetation. For advice and information on soils, altered over time by climate and vegetation. For advice and information on soils,

consult state agricultural experiment stations and their publicationsconsult state agricultural experiment stations and their publications ..