Soils

Why is soil important?

What are indicators of soil health?

***Soil Texture By Feel*** [% Sand, Silt, and Clay]

Soil Horizons:

O: organic

A: Accumulating Layer (top soil) temperate soils can be 10-20% Organic Matter; Tropical Soils: 5% organic matter

E: Elluvaition layer: leaching of nutrients by water

B: Banking Layer: Subsoil- leach nutrients trapped here

C: Chemical Layer: broken, weathered rock

R: Parent material

Physical Properties of Soil: Sand, Silt, Clay *50% pore space is ideal for water/air exchange

Chemical Properties of Soil: Cation Exchange Capacity (CEC): soil loosely holds positive charged particles and exchanges them in plant roots

• clay and Soil Organic matter increase the CEC

• pH effects the availability of nutrients

Biological Properties of Soil: dependent on what is growing

ideal temperature 70-100 F

not too much water

at pH < 6.0 fungal dominate

Humus: stable part of soil organic matter after plants and animals residues have decomposed

= holds water; lots of pore spaces; 2-3% in soils it is hard to increase because lots of material is needed and biological activity continues to cycle it

Management: "AMO" Add Organic Matter (food for microbs; increases carbon content; improves structure and porosity and helps aggregates formation).

To build soil:

• grow plants!

• lay green and brown vegetation on top

• manage water: keyline plow; swales on contour

• crop rotation

• alley cropping

• compost

• cover crops