The Soil SystemThe Soil System1. Read over this presentation2. Read over the questions that come at the end3. Read the assigned pages from the book4. Check out the links provided5. Answer the questions that come at the end.

Who Cares About Dirt?Who Cares About Dirt?

• Soil is the source of nutrients for plants and Soil is the source of nutrients for plants and the basis for root systemsthe basis for root systems

• Soil is the habitat for millions of species of Soil is the habitat for millions of species of plants, microorganisms, and plants, microorganisms, and macroorganismsmacroorganisms

• Soil also acts as a filter, as a recycling Soil also acts as a filter, as a recycling system, and as a pollution control system, and as a pollution control mechanism mechanism

What is Dirt?What is Dirt?• The Soil System integrates biotic and abiotic components The Soil System integrates biotic and abiotic components • The Soil System also integrates other systems!! i.e. lithosphere, The Soil System also integrates other systems!! i.e. lithosphere,

atmosphere, and hydrosphereatmosphere, and hydrosphere

• Soil is a complex mixture of Soil is a complex mixture of - eroded rockeroded rock- mineral nutrientsmineral nutrients- decaying organic matterdecaying organic matter- WaterWater- air air - and billions of living organisms (microscopic decomposers).and billions of living organisms (microscopic decomposers).

• HUMUS -HUMUS - partially decomposed organic matter; the organic partially decomposed organic matter; the organic component of soil component of soil

Soil formation is a slow process:Soil formation is a slow process:

1.1. Weathering of rock (mechanical).Weathering of rock (mechanical).2.2. Deposition of sediments by erosion Deposition of sediments by erosion

(mechanical).(mechanical).3.3. Decomposition of organic matter in dead Decomposition of organic matter in dead

organisms (chemical).organisms (chemical).

SOIL HORIZONS:SOIL HORIZONS:

Mature soils are arranged in a series of zones Mature soils are arranged in a series of zones called SOIL HORIZONS:called SOIL HORIZONS:

““OO”” HORIZON HORIZON = freshly fallen and partially = freshly fallen and partially decomposed leaves, twigs, animal waste. decomposed leaves, twigs, animal waste. You can find fungi and other organic You can find fungi and other organic materials.materials.

““AA”” HORIZON HORIZON = porous mixture of partially = porous mixture of partially decomposed organic matter (decomposed organic matter (humushumus) and ) and some inorganic mineral particles. Also some inorganic mineral particles. Also called TOPSOIL.called TOPSOIL.

MORE SOIL HORIZONS:MORE SOIL HORIZONS:

““BB”” HORIZON HORIZON = has less oxygen due to its = has less oxygen due to its depth below the surface. SUBSOILdepth below the surface. SUBSOIL

““CC”” HORIZON HORIZON = consists of sand, clay, or = consists of sand, clay, or pebbles and rocks. Very little living or dead pebbles and rocks. Very little living or dead organic matter. Often yellow or orange. organic matter. Often yellow or orange. PARENT MATERIALPARENT MATERIAL

These top two layers are most fertile, have the highest These top two layers are most fertile, have the highest concentration of organic matter, and contain large amounts of concentration of organic matter, and contain large amounts of

living organisms.living organisms.

Flatworm

Rove beetle

AntCentipede

Mite

Pseudoscorpion

Groundbeetle

Adultfly

Millipede

Flylarvae

Sowbug

Mite

Earthworm

Slug

Snail

Roundworms

Protozoa

Bacteria

Organic debris

Beetle Mite

Fungi

Springtail

Actinomycetes

Soil ParticlesSoil Particles

• ClayClay (very fine particles) (very fine particles)• Silt Silt (fine particles)(fine particles)• Sand Sand (medium-size particles)(medium-size particles)• Gravel Gravel (coarse to very coarse particles)(coarse to very coarse particles) SOIL TEXTURESOIL TEXTURE is determined by the relative is determined by the relative

amounts of the different types and sizes of amounts of the different types and sizes of mineral particles.mineral particles.

100%clay

Increasingpercentage silt

Increasingpercentage clay

0

20

40

60

80

80

60

40

20

0100%sand 80 60 40 20 100%silt

Increasing percentage sand

sandyclay

clay

siltyclay

silty clayloam

clayloam

loam siltyloam

silt

sandy clayloam

sandyloam

loamy sandsand

Soil Texture Triangle

SOIL POROSITYSOIL POROSITY

• Soil texture helps determine Soil texture helps determine SOIL POROSITYSOIL POROSITY- the measure of the volume of pores or spaces per volume of soil and the measure of the volume of pores or spaces per volume of soil and

the average space between those spaces.the average space between those spaces.

• INFILTRATIONINFILTRATION is the downward movement of is the downward movement of water through soils.water through soils.

• As the water seeps down, it dissolves various soil As the water seeps down, it dissolves various soil components in upper layers and carries them components in upper layers and carries them down to lower layers in a process called down to lower layers in a process called LEACHINGLEACHING..

SOIL PERMEABILITYSOIL PERMEABILITY is the rate at which is the rate at which water and air move from upper to lower soil water and air move from upper to lower soil

layers.layers. Water Water

High permeability Low permeability

Properties of Soils with Different Textures

Texture Nutrient Capacity

Infiltration Water-Holding Capacity

Aeration Workability

Clay Good Poor Good Poor Poor

Silt Medium Medium Medium Medium Medium

Sand Poor Good Poor Good Good

Loam Medium Medium Medium Medium medium

Take a brief pause......

Quick ReviewQuick Review

• Where does SOIL come from??Where does SOIL come from??

• From rocksFrom rocks• Decayed plantsDecayed plants• Decayed animalsDecayed animals• AirAir• WaterWater• LIFE!!LIFE!!

SOIL DEVELOPMENTSOIL DEVELOPMENT

• Soil is not made overnight!!!!Soil is not made overnight!!!!• Results from many years of Results from many years of weatheringweathering• ALL the loose weathered material on the surface of the ALL the loose weathered material on the surface of the

Earth is called the Earth is called the REGOLITHREGOLITH --- soil is the top layer that --- soil is the top layer that supports plant growthsupports plant growth

• Soil layer is 1m to 3m deepSoil layer is 1m to 3m deep• Soil varies from place to place depending on its Soil varies from place to place depending on its

COMPOSITIONCOMPOSITION and and PARENT ROCKPARENT ROCK

WEATHERINGWEATHERING

• The process where big rocks are broken The process where big rocks are broken down into smaller rocks is referred to as down into smaller rocks is referred to as WEATHERINGWEATHERING

• There are 2 main types:There are 2 main types:1.1. MechanicalMechanical2.2. ChemicalChemical

Mechanical WeatheringMechanical Weathering

• Predominates in severe environmentsPredominates in severe environments• No chemical changesNo chemical changes• Cracks or abrades rocks (e.g., glaciers)Cracks or abrades rocks (e.g., glaciers)• Produces coarse textured soilsProduces coarse textured soils• Creates new surfaces for chemical weatheringCreates new surfaces for chemical weathering

Mechanical WeatheringMechanical Weathering1.1. Ice wedgingIce wedging2.2. Plant weatheringPlant weathering3.3. Animal weatheringAnimal weathering4.4. Temperature changeTemperature change5.5. Water abrasionWater abrasion6.6. Wind abrasionWind abrasion

Chemical weatheringChemical weathering

• Involves chemical changeInvolves chemical change– Conversion from primary to secondary mineralConversion from primary to secondary mineral

• Promoted by water and heatPromoted by water and heat• Depends on parent materialDepends on parent material• Stimulated by acidityStimulated by acidity

– What are main acids in soils?What are main acids in soils?

Chemical weatheringChemical weathering

• Reactions Reactions – Acid-baseAcid-base– OxidationOxidation– ChelationChelation

• Environment for weatheringEnvironment for weathering• Susceptibility to weatheringSusceptibility to weathering

Chemical WeatheringChemical Weathering1.1. OxidationOxidation2.2. WaterWater3.3. CarbonationCarbonation4.4. Sulfuric acidSulfuric acid5.5. Plant and fungal acidsPlant and fungal acids6.6. LeachingLeaching – where water carries minerals deeper into – where water carries minerals deeper into

the ground. the ground.

Soil PropertiesSoil Properties1.1. Particle ShapeParticle Shape – – roundround, , flatflat, or , or angularangular. The shape . The shape

affects the affects the porosityporosity of the soil of the soil2.2. Particle SizeParticle Size – – clayclay——siltsilt——sandsand 3.3. FertilityFertility – depends on the amount of dissolved – depends on the amount of dissolved

nutrients in the soil. Some come from bacteria, and nutrients in the soil. Some come from bacteria, and others from bedrockothers from bedrock

4.4. Acid LevelAcid Level – depends on – depends on 5.5. organic matter and organic matter and 6.6. minerals in bedrock. minerals in bedrock.

Affects plant growthAffects plant growth

Generic soil profileGeneric soil profile

Relationships among soil orders

Nitrogen fixingby lightning

Commercialinorganicfertilizer

10-6-4N-P-K

Organic fertilizers,animal manure,

green manure, compost

Cropplant

Deadorganic matter

Applicationto land

Nitrogen fixingby bacteria

Nitrogen fixing

Weatheringof rock

Nutrient removalwith harvest

Decomposition

Supply ofavailable plant

nutrients in soilNutrient lossby bacterialprocesses

such asconversion

of nitrates tonitrogen gas

Nutrient lossfrom soil erosion

Absorption of nutrientsby roots

Pathway of plant

nutrients in soil.

Soil ErosionSoil Erosion

Soil erosionSoil erosion is the movement of soil components, is the movement of soil components, especially surface litter and especially surface litter and topsoil.topsoil.

• The two main agents of erosion are The two main agents of erosion are windwind and and flowing waterflowing water. .

• Loss of plant coverLoss of plant cover by farming, logging, by farming, logging, construction, overgrazing by livestock, off-road construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation and vehicles, deliberate burning of vegetation and other activities leave soil vulnerable to erosion.other activities leave soil vulnerable to erosion.

Two major harmful effects of soil erosion:Two major harmful effects of soil erosion:1.1. Loss of soil fertility and its ability to hold Loss of soil fertility and its ability to hold

waterwater2.2. Runoff of sediment that pollutes water, kills Runoff of sediment that pollutes water, kills

fish and shellfish, and clog irrigation ditches, fish and shellfish, and clog irrigation ditches, boat channels, reservoirs, and lakes.boat channels, reservoirs, and lakes.

serious concern

some concern

Stable areas

Desertification Desertification is the enlargement of is the enlargement of deserts through human activities.deserts through human activities.

ConsequencesCauses

Worsening drought

Famine

Economic losses

Lower living standards

Environmentalrefugees

Overgrazing

Deforestation

Surface mining

Erosion

Salinization

Soil compaction

SALINATION1. Irrigation water contains

small amounts of dissolved salts.

2. Evaporation and transpiration leave salts behind.

3. Salt builds up in soil.

WATERLOGGING• Precipitation and

irrigation water percolate downward.

• Water table rises.

Both result in stunted plant growth, lower crop yields,

dead plants and ruined land.

EvaporationEvaporation

Transpiration

Evaporation

Waterlogging

Less permeableclay layer

Soil ConservationSoil Conservation involves reducing involves reducing soil erosion and restoring soil fertility.soil erosion and restoring soil fertility.

Advantages Disadvantages

Reduces erosion

Saves fuel

Cuts costs

Holds more soil water

Reduces soil compaction

Allows several crops per season

Does not reduce crop yields

Can increase herbicide use for some crops

Leaves stalks that canharbor crop pests and fungal diseases and increase pesticide use

Requires investment in expensive equipment

Advantages and disadvantages of using Conservation Tillage.

http://www.ncsu.edu/sustainable/tillage/tillage.html

Contour plantingContour planting and and strip cropping:strip cropping: each each row acts as a small dam to help hold soil and row acts as a small dam to help hold soil and

slow water runoff.slow water runoff.

http://www.peisland.com/agrtour/xslope.html

Alley cropping or agroforestry:Alley cropping or agroforestry: several crops are several crops are planted together in strips or alleys between trees and planted together in strips or alleys between trees and shrubs that can provide fruit or fuel-wood, shade, help shrubs that can provide fruit or fuel-wood, shade, help retain and slowly release soil moisture, and fodder for retain and slowly release soil moisture, and fodder for

livestock.livestock.

Windbreaks or shelterbeltsWindbreaks or shelterbelts of trees reduce wind erosion, of trees reduce wind erosion, help retain soil, supply wood for fuel, and provide habitats help retain soil, supply wood for fuel, and provide habitats

for birds, pest-eating and pollinating insects, and other for birds, pest-eating and pollinating insects, and other animals.animals.

TerracingTerracing retains retains water for crops at water for crops at

each level and each level and reduces soil erosionreduces soil erosionby controlling runoff.by controlling runoff.

Soil RestorationSoil Restoration Organic fertilizerOrganic fertilizer Animal manureAnimal manure Green manureGreen manure CompostCompost Crop rotationCrop rotation Commercial inorganic fertilizerCommercial inorganic fertilizer

Dirty Questions1. Use a systems approach to draw diagrams that show links between

the soil, lithosphere, atmosphere and living organisms.

2. The soil as a living system should be considered with reference to a generalized soil profile.

3. Transfers of material (including deposition) result in reorganization of the soil. There are inputs of organic and parent material, precipitation, infiltration and energy. Outputs include leaching, uptake by plants and mass movement. Transformations include decomposition, weathering and nutrient cycling. Make a flow diagram that represents this. LABEL ALL FLOWS AND STORAGES.

More Dirty Questions4. Compare and contrast the structure and properties of sand, clay and

loam soils, including their effect on primary productivity. Consider mineral content, drainage, water-holding capacity, air spaces, biota and potential to hold organic matter, and link these to primary productivity. How do all these factors influence NPP? You may want to organize this into a table.

5. Human activities such as overgrazing, deforestation, unsustainable agriculture and irrigation cause processes of degradation. These include soil erosion, toxification and salinization. Desertification (enlargement of deserts through human activities) can be associated with this degradation. Make a table of soil degradation causes, consequences, and possible solutions/clean up that can be performed.

More Dirty Questions6. Evaluate the following soil conservation measures:• soil conditioners (for example, use of lime and organic materials)• wind reduction techniques (wind breaks, shelter belts, strip

cultivation)• cultivation techniques (terracing, contour plowing)• efforts to stop plowing of marginal lands.

7. a) What’s the story behind the green revolution? b) What are some limitations to expanding it?

Check This Site Out!!!

• http://www.globalchange.umich.edu/globalchange2/current/lectures/land_deg/land_deg.html