Chapter 15/14
Soil Resources

Soil
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Uppermost layer of Earth’s crust that supports plants, animals and microbes
Soil Forming Factors
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Parent Material
Time
Climate
Organisms
Topography

Soil Composition
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(45%) Mineral
Particles
Weathered rock
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(5%) Organic
Material Litter
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(25%) Water
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(25%) Air

Soil Organisms
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Soil organisms provide ecosystem services

Nutrient Cycling

Soil Properties

Soil Problems
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1. Soil Erosion
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Caused primarily by water and wind
Why a problem?
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Causes a loss in soil fertility as organic material and nutrients are eroded
More fertilizers must be used to replace nutrients lost to erosion
Accelerated by poor soil management practices

The Dust Bowl

Soil Problems
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2. Nutrient Mineral Depletion

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Suppress plant diseases and pests.
Reduce or eliminate the need for chemical fertilizers.
Promote higher yields of agricultural crops.
Facilitate reforestation, wetlands restoration, and habitat revitalization efforts by amending contaminated, compacted, and marginal soils.
Cost-effectively remediate soils contaminated by hazardous waste.
Remove solids, oil, grease, and heavy metals from stormwater runoff.
Capture and destroy 99.6 percent of industrial volatile organic chemicals (VOCs) in contaminated air.
Provide cost savings of at least 50 percent over conventional soil, water, and air pollution remediation technologies, where applicable.

Soil Problems
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3. Soil Salinization
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Gradual accumulation of salt in the soil, usually due to improper irrigation techniques
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Often in arid and semi-arid areas
Salt concentrations get to levels toxic to plants

Soil Problems
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4. Desertification
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Conversion of productive grassland or woodland into a desert-like region in which little grows
Result of poor agricultural practices or overgrazing

Desertification Around the
World
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Desertification now threatens vast areas
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Africa: Sahara desert is expanding south due to overgrazing
Northwest China: Gobi desert is expanding due to overgrazing and overplowing
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The best way to avoid desertification:
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Avoid farming and grazing in areas with high winds and periodic drought

Modern Dust Clouds

Soil Conservation
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1. Conservation Tillage
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Residues from previous year’s crops are left in place to prevent soil erosion
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2. Crop Rotation
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Planting a series of different crops in the same field over a period of years

Soil Conservation
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3. Contour Plowing
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Strip Cropping
Plowing around hill instead of up-down
Strip Cropping-
Alternating strips of different crops along natural contours
Terracing
4. Terracing
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Creating terraces on steep slopes to prevent erosion

Preserving Soil Fertility
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Organic fertilizers
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Animal manure, crop residue, bone meal and compost
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Nutrient available to plants only as material decomposes (last long, slow acting)
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Inorganic fertilizers
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Manufactured from chemical compounds
Soluble
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Fast acting, short lasting
Mobile- easily leach and pollute groundwater
Problems:
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Leach into groundwater
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Run-off
Don’t hold water well
Contain N gas
Requires energy to make

Soil Reclamation
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1.
2.
Two steps
Stabilize land to prevent further erosion
Restoring soil to former fertility
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Best way to do this is shelterbelts
Row of trees to reduce wind erosion

Soil Conservation Policies in US
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Soil Conservation Act 1935
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Food Security Act (Farm Bill) 1985

Sustainable Use of Biological
Wealth
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Excluding cattle from riparian zones
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Flood protection
Water conservation
Habitat for wildlife
Preservation of biodiversity

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Riparian Restoration
San Pedro River before and after restoration