let’s dish some dirt! please get out paper for notes. please read the board

Let’s dish some dirt!Let’s dish some dirt!

Please get out Please get out paper for notes.paper for notes.

Please read the Please read the board.board.

Dishing the dirt! Dishing the dirt!

Soil ResourcesSoil Resources

complex mixture of inorganic minerals (clay, silt, sand), decaying matter, & living organisms.

•potentially renewable resource;

• typically 200–1000 years to form 2.5 centimeters (1 inch) of topsoil.

© Brooks/Cole Publishing Company / ITP

Soil formationSoil formationPhysicalPhysical

Freeze/thaw cycleFreeze/thaw cycle Weathering/erosionWeathering/erosion

Biological Biological Lichen actionLichen action DecompositionDecomposition

The granite rock cracks and breaks off as it is The granite rock cracks and breaks off as it is heated and cooled each day and season. This heated and cooled each day and season. This

is the first step in the formation of soil.is the first step in the formation of soil.

Physical: Freeze/thaw cyclePhysical: Freeze/thaw cycle

Decomposition: adding carbon, N,P,K Decomposition: adding carbon, N,P,K during soil formationduring soil formation

Soil Food Webs are complex!Soil Food Webs are complex!


• soil food webs complex;• figure shows simplified soil food web.

Fig. 13–15

Soil Nutrient CyclingSoil Nutrient Cycling


pathways of nutrients in soils

Fig. 5–15

Generalized Soil ProfileGeneralized Soil Profile


• O horizon: leaf litter

• A horizon: topsoil

• B horizon: subsoil

• C horizon: parent material bedrock

Examples of Soil ProfilesExamples of Soil Profiles

Fig. 13–17 a & b


More Examples of Soil ProfilesMore Examples of Soil Profiles

Fig. 13–17 c & d


Ecosystem comparison!Ecosystem comparison!

Prairies – rich soil (deep, lots of humus, Prairies – rich soil (deep, lots of humus, nutrients)nutrients)

Tropical Rainforests – poor soils! Rapid Tropical Rainforests – poor soils! Rapid decomposition increases rate of nutrient decomposition increases rate of nutrient uptake!uptake!

Soil types determined by Soil types determined by

Particle sizeParticle size Chemical composition (bedrock material)Chemical composition (bedrock material) ColorColor pHpH

Soil textureSoil texture

Sand Sand Silt Silt ClayClay

Landfills?Landfills? Wetlands?Wetlands?

Soil TextureSoil Texture


determined by particular mix of clay, silt, & sand

Fig. 13–18

ErosionErosion

movement of soil, especially litter & topsoil, from one place to another

•makes soil less fertile & less able to hold water;

• topsoil eroding faster than it forms in about one–third of the world's cropland.


Soil ErosionSoil Erosion

Fig.13–20© Brooks/Cole Publishing Company / ITP

1930s Dust Bowl1930s Dust Bowl

Fig.13–21© Brooks/Cole Publishing Company / ITP

DesertificationDesertificationcauses:• overgrazing;• deforestation &

devegetation;• surface mining;• poor irrigation;• salt buildup;• farming

unsuitable terrain;

• soil compaction.

Fig.13–22


Problems of IrrigationProblems of Irrigation

© Brooks/Cole Publishing Company / ITPFig.13–23

• Salinization: salts build up to levels that decrease yields or prevent cultivation

• Waterlogging excess irrigation water raises water table & lowers crop productivity

Soil ConservationSoil Conservationreduces soil erosion & restores fertility

some methods:

• conservation–tillage

• terracing, contour farming, strip cropping, alley cropping

• organic fertilizers

• crop rotation


Conservation-Tillage FarmingConservation-Tillage Farming

• minimizes soil disturbance

• uses special tillers or no–till methods that inject seeds, fertilizers, & herbicides in unplowed soil

• poses new problems of heavy herbicide use


Some Means to Prevent ErosionSome Means to Prevent Erosion

• terracing protects steep slopes

• contour farming follows natural land contours

• strip cropping maintains strips of different vegetation between crops

• alley cropping grows crops between rows of trees


• organic fertilizers: manure, "green manure" = plant matter, & compost

• decreased use of inorganic fertilizers

• crop rotation: alternating between different crops & fallow times; planting crops that restore nutrients

Some Means to Prevent Soil DegradationSome Means to Prevent Soil Degradation


Pesticides – Pesticides – “To use or not to use?”“To use or not to use?”

What you already know about What you already know about pesticides . . . .pesticides . . . .

The case FOR The case FOR pesticidespesticides

The case AGAINST The case AGAINST pesticidespesticides

A spectrum of choicesA spectrum of choices

Conventional Conventional Integrated PestIntegrated Pest OrganicOrganic Biodynamic Biodynamic

AgricultureAgriculture managementmanagement farmingfarming agriculture agriculture

Least sustainableLeast sustainable most sustainablemost sustainable

Integrated pest managementIntegrated pest management

Overarching philosophy:Overarching philosophy: Eradication of pests is not possible, so the Eradication of pests is not possible, so the

goal must be pest suppression.goal must be pest suppression.

General practice: Monitor pest populations. General practice: Monitor pest populations. When damage of crops will cost more than When damage of crops will cost more than the cost of action, IPM managers take steps the cost of action, IPM managers take steps to control pests. Pesticides will be used only to control pests. Pesticides will be used only as a last resort.as a last resort.

Cultivation/physical Cultivation/physical approachesapproaches

Crop rotation – Crop rotation – non-legume, legume, fallow field/cover cropnon-legume, legume, fallow field/cover crop

Cultivation/physical approachesCultivation/physical approaches

Hedge rowsHedge rows

provide shelter forprovide shelter for

beneficial insects, birds beneficial insects, birds and other pest and other pest predatorspredators

Cultivation ApproachesCultivation Approaches

Delayed planting Delayed planting

If the pest can’t find the If the pest can’t find the crop at the right part crop at the right part of it’s life cycle, the of it’s life cycle, the pest can’t use the pest can’t use the crop.crop.

Cultivation ApproachesCultivation Approaches

Polyculture, Polyculture, intercropping intercropping and and agroforestry – agroforestry – increasing increasing diversity of diversity of crops!crops!

Biological pest controlBiological pest control

Release beneficial Release beneficial insects (pestinsects (pest

predators), predators),

encourage encourage insectivorous insectivorous birdsbirds

Other predatorsOther predators

Biological Pest controlBiological Pest control

Release of sterile Release of sterile males: mate with males: mate with females, no offspring females, no offspring produced.produced.

Chemical Pest controlChemical Pest control

Pheromones: used in Pheromones: used in bait traps to lure bait traps to lure insects away from insects away from cropscrops

Chemical controlChemical control

Hormone disruptors prevent molting or Hormone disruptors prevent molting or development to next stage.development to next stage.

Chemical controlChemical control

As a last resort, IPM farmers will use As a last resort, IPM farmers will use pesticides (herbicides, insecticides, pesticides (herbicides, insecticides, rodenticides, fungicides)rodenticides, fungicides)

IPM approachesIPM approaches

AdvantagesAdvantages DisadvantagesDisadvantages

let’s dish some dirt! please get out paper for notes. please read the board

Documents

soil types

anothermakes soil

formation of soil

erosionmovement of soil

prairies rich soil

soil formationsoil food

simplified soil food

subsoilc horizon