soil resources chapter 15. what is soil? composed of: mineral matter organic matter modified by:...

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