Soil Environment

1) Physical factors: 1.1)Soil Texture Sand (0.05-2.0 mm) Silt (0.002-0.05mm) Clay ( < 0.002mm) 1.2)Soil Density

1.3)Soil Pores Soil pores play a major role in water and air movement. Also, soil microorganisms reside in pores. Pore Size Distribution Macropores ( >75um) Mesopores ( 30-70um) Micropores ( 5-30um) Ulltramicropores (0.1-5um) Crytopores ( <0.1um)

1.4)Soil structure Aggregation of primary soil particles is a critical determinant of soil structure. 2) Soil Environmental 2.1) Abiotic factors 2.1.1)Soil water

Soil water is essential for soil microorganisms. Without some water, there is no microbial activity.

2.1.2)Soil aeration Soil aeration measures how well a soil is oxygenated. Ideally,,a well-aerated soil would have sufficient oxygen for the respiration of plant roots and the function of most aerobic microorganisms. 2.1.3)Soil temperature Soil temperature greatly influences the rates of biological, physical, and chemical processes in the soil.Within a limited range, the rates of chemical reactions and biological processes double for every 10o increase 2.1.4)Toxins poisonous substance produced by living cells or organisms that is active at very low concentrations. 2.1.5)Osmotic pressure Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute. 2.1.6)PH Soil pH is important because microorganisms and plants respond markedly to chemicals in their environment. Most soil microorganisms and plants prefer a near-neutral pH range of 6 to 7 because the availability of most soil nutrients is best in this pH range. 2.1.7)Bioavailability Bioavailability is the amount of a contaminant that is absorbed from soil. 2.2)Biotic factors 2.2.1)Native vegetation

2.2.2)Microflora

2.2.3)Microfauna

2.2.4)Macrofauna

2.2.5)Anthropogenic (producing human, farming)