Chapter 15 Soil Resources
What is Soil? Composed of: mineral matter organic matter Modified by: weather water organisms
What is Soil? How Soils are Formed From parent material Formation time varies (200 – 1000 years) Depth varies (thin film to 10 ft)
What is Soil? Soil Composition
What is Soil? Soil Composition Other components: Humus
What is Soil? Soil Composition Other components: Pore space (wet soil) Pore space (dry soil)
What is Soil? Soil Horizons
What is Soil? Soil Organisms
What is Soil? Nutrient Cycling
What is Soil? Nutrient Cycling (alternate slide) Elements in organic matter in animals Elements incorporated into organic matter in plants Organic matter in soil Decomposition Minerals freed and available to plant Plant roots absorb minerals from soil
Soil Properties and Major Soil Types Soil Texture: Sand, Silt, and Clay
Soil Properties and Major Soil Types Availability of nutrient minerals in clay
Soil Properties and Major Soil Types Soil Properties Affected by Soil Texture
Soil Properties and Major Soil Types pH scale Soil Acidity Pygmy Forest Most soils (pH = 4-8) 7 Death Valley 14
Soil Properties and Major Soil Types Major Soil Groups
Soil Properties and Major Soil Types Major Soil Groups
Soil Properties and Major Soil Types Major Soil Groups
Soil Problems Soil Erosion Caused by water, wind, and ice
Soil Problems Case-in-Point: The American Dust Bowl
Soil Problems Nutrient Mineral Depletion
Soil Problems Soil Problems in the United States Cultivated soils in southern Iowa, northern Missouri, western and southern Texas, & eastern Tennessee have greatest erosion 25% of agricultural lands lose more topsoil than formed
Soil Problems World Soil Problems Mineral depletion in tropical rainforest soils Degradation in the African Sahel
Soil Conservation and Regeneration Conservation Tillage
Soil Conservation and Regeneration Crop Rotation ALFALFA 4th Year OATS 3rd Year CORN 1st Year SOYBEANS 2nd Year
Soil Conservation and Regeneration Contour Plowing, Strip Cropping, and Terracing Terracing Strip cropping & contour plowing
Soil Conservation and Regeneration Preserving Soil Fertility Organic fertilizers e.g., manure, compost slow release, but nutrient content varies Commercial inorganic fertilizers e.g., typical bagged fertilizer exact nutrient content known, but prone to leaching
Soil Conservation and Regeneration Soil Reclamation increasing productivity on eroded land Shelterbelts