The document defines soil in several ways and discusses its key components and formation processes. Soil is defined as the unconsolidated mineral and organic material on Earth's surface that supports plant growth. It is formed through translocations, transformations, additions and losses of materials over time under the influence of parent material, climate, biota, topography and time. The main components of soil are minerals, organic matter, water and air. Organic matter accumulation is important for soil fertility and health.

1. Natural
Resources
Conservation
Service
Helping People Help the Land

2. SOIL ANDSOIL AND
SOILCONCEPTSSOILCONCEPTS
BYBY
ALLAH DAD KHANALLAH DAD KHAN
(FOurTH PrESENTATION)(FOurTH PrESENTATION)

3. Soil Definition (SSCA) Soil Definition (SSCA)
(i)(i) The unconsolidated mineral or organic material on the immediateThe unconsolidated mineral or organic material on the immediate
surface of the Earth that serves as a natural medium for the growthsurface 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 ofii) The unconsolidated mineral or organic matter on the surface of
the Earth that has been subjected to and shows effects of geneticthe Earth that has been subjected to and shows effects of genetic
and environmental factors of: climate (including water andand environmental factors of: climate (including water and
temperature effects), and macro- and microorganisms, conditionedtemperature 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

4. Soil Definition(STSE)Soil Definition(STSE)
Soil is a natural body comprised of solids (minerals and organicSoil is a natural body comprised of solids (minerals and organic
matter), liquid, and gases that occurs on the land surface, occupiesmatter), 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 materialhorizons, or layers, that are distinguishable from the initial material
as a result of additions, losses, transfers, and transformations ofas a result of additions, losses, transfers, and transformations of
energy and matter or the ability to support rooted plants in a naturalenergy and matter or the ability to support rooted plants in a natural
environment.environment.
Source (Soil Taxonomy, second edition)Source (Soil Taxonomy, second edition)

5. 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.

6. Soil Traditional Definition Soil Traditional Definition
Material which nourishes and supports growing plants; includesMaterial which nourishes and supports growing plants; includes
rocks, water, snow, air.rocks, water, snow, air.

7. 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.

8. Soil Taxonomy Definition Soil Taxonomy Definition
 Collection of natural bodies of the earth’s surface, in places modifiedCollection of natural bodies of the earth’s surface, in places modified
or even made by man or earthy materials, containing living matteror 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 depthIts 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.

9. Soil Health and Ecosystem Soil Health and Ecosystem
Soil health is an assessment of ability of a soil to meet its range ofSoil health is an assessment of ability of a soil to meet its range of
ecosystem functions as appropriate to its environment. Also refersecosystem 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 Soilnutrients, and microbial activity), pH, and structure. The Soil
Science Society defines soil health as the capacity of a specific kindScience 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 waterto 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

10. Soil Health and Ecosystem contdSoil Health and Ecosystem contd
Ecosystems that benefit humans. Collectively, these benefits areEcosystems that benefit humans. Collectively, these benefits are
known as ecosystem services and include products like cleanknown 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.

11. Oganic MatterOganic Matter
 Classified into two major groups composing a humic and non-humicClassified into two major groups composing a humic and non-humic
substances. Soil organic matter is thermodynamically unstable andsubstances. 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. Thetransformation, and resynthesis of various organic substances. The
humified fraction is composed of humic, fulvic, and humin and is thehumified fraction is composed of humic, fulvic, and humin and is the
most stable. The non-humic portion is the relatively unstable andmost 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. SoilSoil Organic Carbon: Is related directly to soil organic matter. Soil
organic matter consists of 50 to 58 percent soil organic carbon. Aorganic matter consists of 50 to 58 percent soil organic carbon. A
simple unit of 1.724 is used to convert total carbon into soil organicsimple unit of 1.724 is used to convert total carbon into soil organic
mattermatter

12. Soil As a portion of the landscapeSoil As a portion of the landscape
Collection of natural bodies occupying portions of the earth’sCollection of natural bodies occupying portions of the earth’s
surface that support plants and that have properties due to thesurface that support plants and that have properties due to the
integrated effect of climate and living matter, acting upon parentintegrated 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.

13. Soil Forming ProcessesSoil Forming Processes
 TranslocationsTranslocations
 TransformationsTransformations
 AdditionsAdditions
 LossesLosses

14. 1.Translocation1.Translocation
Translocation refers to the physical movement of material withinTranslocation refers to the physical movement of material within
soil. The material can be in the solid, liquid or gaseous form, thesoil. The material can be in the solid, liquid or gaseous form, the
movement can be in any direction from and to any horizon. Formovement can be in any direction from and to any horizon. For
instance clay, organic matter and iron and aluminum hydrous oxidesinstance clay, organic matter and iron and aluminum hydrous oxides
are commonly moved from the surface horizon to a subsurfaceare commonly moved from the surface horizon to a subsurface
horizon. Conversely, in very dry climates salts are moved upwardshorizon. Conversely, in very dry climates salts are moved upwards
in solution by capillarity, and in very cold climates solid mineralin solution by capillarity, and in very cold climates solid mineral
fragments are moved upwards by frost action.fragments are moved upwards by frost action.


15. 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 organictransformation of coarse OM into decay resistant organic
compoundscompounds

16. 3.Addition3.Addition
Materials added to the soil, such as decomposingMaterials added to the soil, such as decomposing
vegetation and organisms (organic matter--OM), or newvegetation and organisms (organic matter--OM), or new
mineral materials deposited by wind or water.mineral materials deposited by wind or water.

17. 4.Losses4.Losses
Through the movement of wind or water, or uptake by plants, soilThrough the movement of wind or water, or uptake by plants, soil
particles (sand, silt, clay, and OM) or chemical compounds can beparticles (sand, silt, clay, and OM) or chemical compounds can be
eroded, leached, or harvested from the soil, altering the chemicaleroded, 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. ForLosses occur both from the surface and from the deep subsoil. For
instance, water is lost by evapotranspiration and carbon dioxide byinstance, water is lost by evapotranspiration and carbon dioxide by
diffusion at the surface and, on a more catastrophic level, largediffusion at the surface and, on a more catastrophic level, large
masses of soil can be stripped by erosion. Materials suspended ormasses 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.

18. Factors of Soil FormationFactors of Soil Formation
The 5 factors of soil formation are:The 5 factors of soil formation are:
 Parent materialParent material
 ClimateClimate
 BiotaBiota
 TimeTime
 TopographyTopography

19. Parent MaterialParent 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 whenWhen 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 issoil 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 ofThere 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 texturedFinely textured parent materials tend to weather into finely textured
soils. Coarsely textured parent materials tend to weather intosoils. 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.

20. 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 allClimate is a fundamental force of weathering that interacts with all
other soil formation factors. The primary forces of climate areother soil formation factors. The primary forces of climate are
precipitation and temperature. While nutrients can be released fromprecipitation and temperature. While nutrients can be released from
primary minerals during weathering, high levels of precipitation andprimary minerals during weathering, high levels of precipitation and
temperature can remove, or leach, nutrients from the soil andtemperature can remove, or leach, nutrients from the soil and
reduce its fertilityreduce its fertility

21. BiotaBiota
Biota is the vegetation that covers the soil, the animals that liveBiota is the vegetation that covers the soil, the animals that live
upon the soil, and the soil microorganisms that inhabit the soil. Soilsupon the soil, and the soil microorganisms that inhabit the soil. Soils
that develop in grasslands will be remarkably different than soils thatthat develop in grasslands will be remarkably different than soils that
develop in forests. This soil formation factor is intimately influenceddevelop in forests. This soil formation factor is intimately influenced
by climate and changes over timeby climate and changes over time..

22. TimeTime
 The soil profile is continually changing and developing with time. In theThe soil profile is continually changing and developing with time. In the
beginning, pioneer species, such as mosses and lichens, colonize rocksbeginning, pioneer species, such as mosses and lichens, colonize rocks
and secrete acids that weather the rocks. Microorganisms, such as bacteriaand secrete acids that weather the rocks. Microorganisms, such as bacteria
and fungi, are instrumental in forming soil through the decomposing organicand fungi, are instrumental in forming soil through the decomposing organic
matter and binding of soil particles. Earthworms create channels, as well asmatter and binding of soil particles. Earthworms create channels, as well as
secrete substrates that bind soil particles together. Animals, as well assecrete substrates that bind soil particles together. Animals, as well as
humans, directly and indirectly transform the soil through their manyhumans, directly and indirectly transform the soil through their many
activities, in both positive and negative ways. Additionally, with time, theactivities, 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.

23. TopographyTopography
 Topography has a direct impact on water drainage. We mayTopography has a direct impact on water drainage. We may
observe the effect of topography by describing a typical mountainobserve the effect of topography by describing a typical mountain
slope. Residual soils that form along the uplands tend to experienceslope. Residual soils that form along the uplands tend to experience
good drainage. The colluvium soils that form along steep slopes willgood drainage. The colluvium soils that form along steep slopes will
usually have excessive drainage. Finally, alluvial soils that form inusually have excessive drainage. Finally, alluvial soils that form in
the flood plains have poorer drainagethe flood plains have poorer drainage..

24. Soil ComponentSoil Component
 Soils are multiphase systems, composed of a mixture of numerousSoils 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 theThe proportions of these components vary from point to point on the
surface of the earth, and from time to time, depending upon thesurface 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)

25. Soil Mineral PortionSoil Mineral Portion
 Particle size of the mineral fraction varies widely, from stones (overParticle size of the mineral fraction varies widely, from stones (over
250 mm in diameter), through cobbles (250-75 mm), gravel (75-2250 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 thanmm), sand (2-0.05 mm), silt (0.05-0.002 mm) to clay (less than
0.002 mm).0.002 mm).

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

27. Role of soil organic matter in cropRole of soil organic matter in crop
productivityproductivity
 a.a. Cation exchange capacityCation exchange capacity
b. Nutrient retention and releaseb. Nutrient retention and release
c. Soil structure and bulk densityc. Soil structure and bulk density
d. Water-holding and snow/drain catchmentd. Water-holding and snow/drain catchment
e. Biological activitye. Biological activity

28. Matson et al. factors affecting soil C loss fromMatson 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

29. Soil WaterSoil Water
 The importance ofThe importance of soil watersoil water lies in its roles in plant growth and inlies in its roles in plant growth and in
the chemical and physical reactions that occur in soils. Waterthe chemical and physical reactions that occur in soils. Water
provides the medium by which plants take up their nutrients inprovides the medium by which plants take up their nutrients in
solution through their root systems; it may also be considered asolution 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

30. Soil AirSoil Air
 Soil airSoil air plays an important role in plant growth and the activity of soilplays an important role in plant growth and the activity of soil
organisms. Its main constituents, as in the atmosphere, areorganisms. Its main constituents, as in the atmosphere, are
nitrogen, oxygen and carbon dioxide. Various organisms use thenitrogen, oxygen and carbon dioxide. Various organisms use the
oxygen and give off carbon dioxide. The supply of oxygen has to beoxygen and give off carbon dioxide. The supply of oxygen has to be
constantly replenished and this is the importance of adequate poreconstantly replenished and this is the importance of adequate pore
spaces or aeration within the soil. For adequate aerationspaces 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.

31. 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

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

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

34. Soil and NutrientsSoil 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 aremagnesium, sodium, and potassium. Factors determining the nature of soil are
vegetation type, climate, and parent rock material; geographic relief and thevegetation type, climate, and parent rock material; geographic relief and the
geological age of the developing soil are also factors. Acidic soils occur in humidgeological age of the developing soil are also factors. Acidic soils occur in humid
regions because alkaline minerals are leached downward: alkaline soils occur in dryregions because alkaline minerals are leached downward: alkaline soils occur in dry
regions because alkaline salts remain concentrated near the surface. Geologicallyregions because alkaline salts remain concentrated near the surface. Geologically
young soils resemble their parent material more than older soils, which have beenyoung 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..