Chapter 8: Soil

Goals Understand how the soil quality determines what can grow Understand how soil quality can determine the survival of societies

Note: Fig. 8-4 in our book also includes the “E horizon”

O Horizon Humus- dark, soft, spongy residue of organic matter as a result of decomposition of organic matter such as leaves and dead wood 1 ۫ source of nutrients in soil systems

A Horizon Top soil-mixture of humus and leachial mineral soil Thin roots extend into this layer

E Horizon Eluviation process of leaching (note: You may see this word spelled with and I, A, or E) Minerals are “leached” into this layer from H 2 O moving downward

Accumulation of elluvial organic matter Often high in iron, aluminum, and calcium Often high in clay content

Unweathered parent material Shows little or no sign of soil formation (primary succession ) Glacial deposits, volcanic ash Reveals history of the land

Texture Sand mm Silt mm Clay.002mm ≥ some microscopic Porosity and Permeability

LOAM: 40%sand 40% silt 20% clay Loam is theoretically the ideal soil ltpwww.gsfc.nasa.gov/ globe/pvg/texture3.htm

Classes of Soil Mollisols - very fertile, dark, found in temperate grasslands, best agricultural soil, Deep A horizon Oxisols - soil of tropical and subtropical rainforest layer of iron and Al oxides in B horizon, little O horizon Alfisols - weathered forest soil, not deep, but developed OAE+B typical of most temperate forest biome. Need fertilizer for agriculture Aridsols - dry lands + desert, lack of vegetation, lack of rain  unstructured vertically, irrigation leads to salinization because of high evaporation.

The Public Policy and Soil Low Input sustainable Agriculture (LISA) -started by US Defense of Agriculture in 1988 Conservation Reserve Program Food Security Act of 1985 Federal Agriculture Improvement and Reform (FAIR) 1996 Environmental Quality Incentive Program (EQUIP) Know these Acts and Laws:

LOAM: 40%sand 40% silt 20% clay Loam is theoretically the ideal soil ltpwww.gsfc.nasa.gov/ globe/pvg/texture3.htm