Soils

Soil is a collection of minerals, air, water, and humus on the earth’s crust that support plant growth

Soils

It is our most precious natural resource. Why?

Functions of Soil

1.Plant growth-soil provides physical support, nutrients, water, and air (CO2 & H2O)

2.Recycle raw material-The decomposition of organic matter returns nutrients to the soil for use by other plants.

Functions of Soil

3.Habitat for soil organisms-This is the home for Billions of organisms both producers and consumers.

4.Engineering medium-Soil effects the types of Building construction activities.

5 Soil Formation Factors

1. Parent material-The material that soils will be formed from.

2. Climatic factors* Most influential of the four factors.

a. Temperature

b. Rain

c. Wind*Active factors

Soil Formation Factors

3. Relief (topography)The elevation or slope of the land.Soil Formation Factors

4. Biota* (biosphere) All Living organisms in an environment

5. Time-The amount of time that materials have been weathered, determine the type of soil and it’s properties.

Soils have three different particle sizes

The largest particles are sand. They range from 2.0-.005 mm in diameter

Soil Structure

Soil Structure

Particles that are between .005-.002 mm in diameter are considered silt.

The soil particles .002 mm in diameter and smaller are clay particles.

Texture Pyramid Sand, silt and clay are compressed together to form

soil aggregates called peds

4 Soil components

Average soils will contain 45% minerals and 5% organic matter.

The components air and water equal the other 50%.

Soil components

The two components Water and Air change depending on the amount of water or rain fall a soil receives.

The four parts of a soil: mineral organic matter (HUMUS) water air

Master Horizons

O-(organic) forms above the mineral soil. This horizon is usually found in forested areas.

A-This is the top soil. It is a dark humus layer where most plant rooting occurs

Master Horizons

B-zone of illuviation or accumulation from zones above it.

C-parent material composed of wind-blown silt(loess),river deposits or glacial till,

R-Bedrock

Transportation of Soils

Gravity-colluvial water

stream-alluvial ocean-marine lake-lacustrine

ice -glacial wind-aeolian

Erosion The largest environmental problem

stemming from agriculture is erosion. Erosion lowers productivity because of

the loss of topsoil.

Erosion Prevention

1. Minimum or No till farming-Leaving stubble in the fields to hold soil and planting over it.

2. Terracing-Planting crops in a zig-zag formation.

The Soil Ecosystem

Interaction of biotic and abiotic factors in a soil environment. The process of organisms growing and decomposing.