SOILSIII. Soils - soil science = PEDOLOGY

A. Most important result of weathering is soil

1. Loose weathered rock - sand, clay, silt

2. Organic material - dead plants and animals, HUMUS

3. Parent material - is what the soil is formed from.

A. residual soil - soil made from local bedrock

B. Transport soil - soil that was moved by wind, or glacier

SOIL B. Factors determining soil makeup

1. Climate - Rainfall amount and temperature (most important)

2. Parent Rock - Type and chemical composition

3. Vegetation - Roots and Leaves

4. Topography - hilliness, etc.

5. Time - how long to develop

SOILS PROFILE

B. Soil Profile - a cross reaction of soil down to the bedrock. Almost all soils show a “profile” of 3 distinct layers or zones (A,B,C)

A. “A (horizon)” topsoil, gray or black, has humus

B. “B (horizon)” subsoil, more clay is washed down

C. “C (horizon)” Rock fragments and slightly weathered bedrock

Note: More detailed description in your packet.

MATURE VS. IMMATURE SOIL

Mature soil is soil that is fully developed! Has a distinguished A,B, and C horizon.Forest soil, Grassland soil, and Tropical Soil

Immature soil is soil that is not fully developed! Does not have a distinguished A,B and C horizon. Ex. Desert soil, Arctic soil

PEDALFERS1. Pedalfers - Found in eastern half of U.S. where rainfall exceeds 25 inches/year

a. Ped - soil / Al - aluminum / Fe - ferrum - iron al from clay , fe from iron oxide

b. Forms in humid climate

1. Moisture produces iron oxide into B horizon

2. Leaching of clay to B horizon

3. Soil becomes acidic

PEDOCALS2. Pedocals – Found In Western Half of U.S. where rainfall is less than 25 in./year

a. Ped – Soil Cal – Calcium

b. Why form in dry climate? THINK!

1. Not much rain but enough (in wet seasons) to leach soluble Calcium and Magnesium into B horizon – but that is as far as it gets.

2. Accumulates in B horizon

3. Therefore Calcium Carbonate (lime) forms in this soil – makes it ALKALINE (basic)

SOIL TYPES AND CLIMATEC. Soil types and climate

1.Most important factor affecting soil is the climate

A. Tropical soil - Warm and wet, speed up chemical weathering. Thus soil forms more quickly. Infertile due to leaching because of rain (high temp. and heavy rainfall). Note: 3 meters

B. Temperate Soil – Due to temperature change there is both chemical and mechanical weathering. Just amount of rain supplied for a thick A horizon. Great for farming!

C. Arctic soils - High elevation and latitude. Very few layers, shallow. Permafrost.

SOIL CONSERVATIONB. SOIL CONSERVATION

1. Soil Erosion - movement of topsoil by water and wind 4 bill tons (water), 1 bill tons (wind) = loss of topsoil

REDUCE IT!!!!

1. Windbreaks (level plains)

2. Contour farming (plant parallel to land contours) prevents gullying

3. Terraces (flattened slopes)

4. Strip cropping (reduces sheet erosion)

5. Crop rotation

CONTOUR FARMING

CROP ROTATION

TERRACING

Wind Breaks