WHY SOILS DIFFER

Soils vary in many ways. They vary in color and weight. Some drain eas­ily whereas others stay wet and bog-like. Some are rocky, breaking tools and backs, while others are easy to dig. Even though the original parent stone may be the same or similar, differences in the subsoil and topsoil may result from variations in:

• weathering elements

• soil movement

• topography

• climate

• amount of organic mater

Soils that weather from bedrock and remain in place are termed sedentary, in contrast to transported soils. Transported soils have been moved by the forces of nature.

1. Colluvial soils have moved in response to gravity, as after a land­slide or mudslide.

2. Alluvial soils are carried in water such as rivers. They are eventu­ally deposited on flood plains and at deltas.

3. Aeolian soils are transported and deposited by winds.

4. Glacial till is soil deposited by glaciers.

The best agricultural soils are usually alluvial and glacial till. Colluvial soils are characterized by coarse textures and other undesir­able chemical and physical qualities. Aeolian soils are finely textured but vary greatly in their productivity. Sedentary soils may be useful for agriculture if they have not lost their nutrient elements.