Chapter 15/14 Soil Resources

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

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

Soil Organisms  Soil organisms provide ecosystem services

Nutrient Cycling

Soil Properties

Soil Problems  1. Soil Erosion  Caused primarily by water and wind  Why a problem?  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  2. Nutrient Mineral Depletion

 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.

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

Soil Problems   4. Desertification   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   Desertification now threatens vast areas   Africa: Sahara desert is expanding south due to overgrazing   Northwest China: Gobi desert is expanding due to overgrazing and overplowing   The best way to avoid desertification:   Avoid farming and grazing in areas with high winds and periodic drought

Modern Dust Clouds

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

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

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

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

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

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

Riparian Restoration   San Pedro River before and after restoration