Unit 4Unit 4Soil ScienceSoil Science

Importance of SoilImportance of Soil

• What is soil?• Holds water and nutrients for plants• Natural filter• Stores and recycles nutrients• Fertile soil = higher yields• Erosion

Soil FormationSoil Formation

• 5 Factors– Parent material– Climate– Biological factors– Topography– Time

Soil ProfileSoil Profile

• O = organic matter or humus

• A = organic and inorganic

• E = little organic matter due to eluviation

• B = leached or washed materials

• C = parent material

Organic and Inorganic Organic and Inorganic SoilsSoils

Organic SoilsComposed mostly of

decayed plant and animal

matter

Inorganic SoilsComposed mostly of minerals

Soil Types and TextureSoil Types and Texture

Soil pHSoil pH• Affects how nutrients

and chemical are absorbed by plants

• Some plants like more acidic soil

• Others prefer a more basic soil

• How is soil pH changed?

Water and Nutrients in Water and Nutrients in the Soilthe Soil

Sand

Sand

SandSand

SandSilt

Silt

Silt

Silt

Silt Silt

Silt

Silt

Clay

Clay

Clay

Clay

Clay

Clay Clay

ClayClay

Clay

Clay

Clay Clay

Clay

Clay

Clay

Clay

Clay

ClayClay

Clay

• Large pore spaces allow water and nutrients to move quickly• Small pore spaces tightly hold onto

water and nutrients

Soil ErosionSoil Erosion

• Topsoil• Nutrients are lost• Water erosion• Wind erosion• Management– Crop rotation– Cover crops– Rotational grazing– Tillage practices

Soil EcosystemsSoil Ecosystems

• Plants

• Burrowing Mammals

• Arthropods

• Earthworms

• Microorganisms