 Soil is the lose covering of rock particles and decaying organic matter(humus)  Results from both physical and chemical weathering

 Regolith - The layer of rock and mineral fragments that cover almost all land as a result of weathering.  Soil is the part that supports the growth of plants.

1. Mineral matter (broken-down rock) 2. Organic matter (humus) 3. Air 4. Water Good soil = at least 50% mineral and organic matter!

 Soils are composed of particles that can be sand, silt or clay sized.  Based on the soils % composition of each type of particle that determines the soils texture

Soil Texture Texture refers to the proportions of different particle sizes. A. Sand (large size) B. Silt – feels like flour C. Clay (small size) D. Loam (a mixture of all three sizes) is best suited for plant life.

1. Clay  fine-grained  deep reddish orange color  Heavy, sticky and plastic-like when wet

2. Silt  smooth and slippery to the touch when wet  individual particles are much smaller than those of sand but larger than clay

3. Sand  gritty to the touch  individual grains or particles seen with the naked eye  coarse in texture

4. Loam  composed of sand, silt, and claysandsiltclay  contains many nutrients  humus- from organic matter decay  gritty, moist, retains water easily  dark in color

 Percentage of open spaces in a given volume of rock or sediment  Open spaces can be: fractures, cavities, or pores  Factors influencing porosity: 1. Sorting-amount of uniformity 2. Way particles are packed-  tightly packed=low porosity  loosely packed=high porosity  Permeability-how freely water passes through open spaces  impermeable-water can not flow through

 Parent material is the source of the mineral matter in soils  Parent material is important because:  It affects the rate of weathering  Chemical makeup affects the soils fertility

 Time-The longer a soil has been forming the thicker it is.  As a soil gets older other characteristics affect the soil more than the parent material

 Climate has the greatest affect on soil formation  Variations in temperature and precipitation affect the rate, depth and type of weathering

 Plants are the main source of organic matter  Plants release nutrients when they decay. Adds to the soils fertility

 Steep slopes have higher erosion. Little water can soak in.  Soils are thin on steep slopes

 A soil profile is the vertical sequence of soil layers  Soil horizons are the distinct layers in a profile  The upper layers contain more organic material, the bottom layers contain more parent material

It consists of leaf litter and other organic material lying on the surface of the soil.

This layer is usually loose and crumbly with varying amounts of organic matter.

This is generally the most productive layer of the soil. Conservation efforts are focused here!

Subsoils are usually lighter in color, dense and low in organic matter.

This layer of transition is almost completely void of organic mater and is made up of partially weathered parent material.

Below the C horizon the unweathered bedrock will be found.

ClaySiltSandType of Soil 20%30% 60%30% 50% 10%70%

 Red clay and heavy clay – improved by adding organic matter.  Leading field crop? Tobacco and cotton

 Peanuts and sweet potatoes  Apples  Hay and wheat