Soils parent material is the material that soil develops from.

Good soil will have roughly 25% air, 25% water, 45% minerals and 5% organic matter. Loam (the ideal farming soil) has clay, sand, and silt in equal proportions.

Soil Formation

Climate The most powerful soil-forming factor. It is both temperature effects and rainfall effects. Temperature controls rates of chemical reactions. Warm-region soils are normally more developed or more mature than are cool-region soils. Rainfall affects leaching, pH and soil aeration. Climate also profoundly affects vegetation which in turn also affects soil formation.

Organisms We affects the soil by: plowing, irrigating, mining, clearing, disposing and leveling. Vegetation as a food source exerts a strong influence on soil microbial populations. Vegetation directly influences the type and amount of organic matter accumulation on the soil, thus influences pH and nutrient supply.

Relief or topography Relief influences erosion. A steep slope will encourage runoff. In the northern hemisphere a north-facing slope will be cooler than a south-facing slope.

Parent Material Effect features like soil texture, pH and mineral constituents. Considered inherited as opposed to acquired.

time Soils change over time. Clays are secondary minerals. They form in the soil, then change forms, and all the while they are moving downward with leaching rainwater. Similarly, organic matter forms on the surface as it moves downward with rainwater.

Soil consists of five major zones (horizons) Soil horizons differ in color, texture, structure, and thickness. Other differences such as chemical and mineral content, consistence, and reaction require special laboratory tests. Soil scientists use the capital letters O, A, B, C, and E to label identified master horizons, and lowercase letters for distinctions of these horizons. Not all horizons are present in every soil.

O Horizon At the top of the profile is the O horizon. The O horizon is primarily composed of organic matter. Fresh litter is found at the surface, while at depth all signs of vegetation structure has been destroyed by decomposition. The decomposed organic matter, or humus, enriches the soil with nutrients (nitrogen, potassium, etc.), aids soil structure (acts to bind particles), and enhances soil moisture retention.

A Horizon Beneath the O horizon is the A horizon. The A horizon marks the beginning of the true mineral soil. In this horizon organic material mixes with inorganic products of weathering. The A horizon typically is dark colored horizon due to the presence organic matter. Eluviation, the removal of inorganic and organic substances from a horizon by leaching occurs in the A horizon. Eluviation is driven by the downward movement of soil water.

E Horizon The E horizon generally is a light-colored horizon with eluviation being the dominant process. Leaching, or the removal of clay particles, organic matter, and/or oxides of iron and aluminum is active in this horizon. Under coniferous forests, the E horizon often has a high concentration of quartz giving the horizon an ashy-gray appearance.

B Horizon Beneath the E horizon lies the B horizon. The B horizon is a zone of illuviation where downward moving, especially fine material, is accumulated. The accumulation of fine material leads to the creation of a dense layer in the soil.

C Horizon The C horizon represents the soil parent material, either created in situ or transported into its present location. Beneath the C horizon lies bedrock. Situ is a Latin phrase meaning in the place. Situ typically describes natural material or processes prior to transport.

Horizons What do you see????

Desertification Caused by the expansion and over use of dry lands. –Poor agricultural practices: overgrazing, over cultivation, improper watering, forest removal, –Non human causes are linked with climate change. Is the caking of exposed topsoil by rain and sun that increases runoff, water erosion and gullying. Soil drying promotes wind erosion and encroachment of sand dunes on arable land. Overgrazing has several effects: –Causes a decline in pasture vegetation. –Compacts soil under trampling hoofs. –Destabilizes dunes when crest vegetation is eaten. Remediation: Reduce overgrazing, plant trees and grasses to hold soil

Salinisation Excessive amounts of water-soluble salts in the soil. Mainly sodium chloride and sodium sulphate. Natural salt accumulation happens through a high salt content of the parent material or in groundwater. Secondary salinisation is caused by human interventions such as with salt-rich irrigation water and/or insufficient drainage. Remediation: take land out of production for 2-5 years, flush soil with freshwater into separate lined evaporation ponds

WATERLOGGING This occurs in poorly drained soils where water can't penetrate deeply. –An impermeable clay layer below the soil can blocks water. When soils are water logged, air spaces in the soil are filled with water, and plant roots essentially suffocate. Remediation: switch to less water- demanding plants, use conservation – tillage farming.