Unit 3 Food: Soil Formation

Soil Development: the starting bedrock material and weathering/erosion processes determine the mixture of components in dirt

Dirt compositions:

1. Iron - Clay, iron oxide

2. Feldspar - Clay, K Na Ca ions

3. Quartz - Quartz

4. Muscovite Mica - Clay, K ions

5. Calcite - Ca, CO ions

Color is used as a guide to let us know what the organic content and chemical compositions of the soil is

• the darker the brown, the more organic matter there is

• Munsell Soil Color Chart

Soil Formation: soil is formed from the weathering of bedrock mixed with the deposition of other eroded rock plus organic materials

Soil Types: sand, silt or clay, these are designated by their size and texture. Categorized by the Soil Texture Triangle

1. Sand: medium sized grains drains excessively

2. Silt: very fine sized grains, drains well

3. Clay: large grains, drains poorly

The USDA Soil Classification guide, uses the soil textures to index what type of water drainage they produce

Arability:

1. Sand - hard to grow

2. Silt Loam - well to grow

3. Sandy Clay, and Clay Loam - hard to grow, need fertilizer or added organic materials

Clay Minerals

1. Some clay minerals have space for water in their crystalline structure

2. Expansive Structure: clay takes in water and expands, once the water dries the clay shrinks

Soil Horizons

1. Horizons: soil develops in layers, which are called horizons. This is a results of weathering and erosion

   1. O Horizon - organic

   2. A Horizon - top soil, high concentration of organic matter (leaching)

   3. B Horizon - subsoil (accumulation)

   4. C Horizon - weathered rock (broken bedrock)

   5. R Horizon - rock

2. Horizons are created in the order of R, C, A, B, the O.

1. Color changes and texture changes from the compositional change

2. Factors that affect soil formation:

   1. Climate

   2. Parent material

   3. Time

   4. Plants and animals

   5. Topography

   6. Humans