soil resources chapter 15. what is soil? composed of: mineral matter organic matter modified by:...
TRANSCRIPT
Soil Resources
Chapter 15
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
Mineral matter
Organic matter
Water
Air
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)
Organic matter in soil
Decomposition
Minerals freed and available to plant
Plant roots absorb minerals from soil
Elements incorporated into organic matter in
plants
Elements in organic matter in
animals
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
Soil AciditypH scale0
7
14
Most soils (pH = 4-8)
Pygmy Forest
Death Valley
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
CORN
1st Year
SOYBEANS
2nd Year
OATS
3rd Year
ALFALFA
4th Year
Soil Conservation and Regeneration
Contour Plowing, Strip Cropping, and Terracing
Strip cropping & contour plowing
Terracing
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