Soil Environment

Introduction

In the Global Warming Age, soil scientists are concerned about a loss of microbial diversity. Microbial populations thrive when they have unlimited space, food, and free energy. Such general requirements can be met in a plethera of different ways depending on the soil environment and physcial factors. This page is dedicated to the exploration of how the soil environment and physical factors control microbial activity.

Key Points

Physical Factors

Soil Texture: Sand (0.05-2.0 mm) Silt (0.002-0.05mm) Clay ( < 0.002mm) Soils that are coarse textured are less likely to have a well-defined structure and therefore fewer structured pore space than s soil high in clay content.

- Soil pores play a major role in water and air movement. Also, soil microorganisms reside in pores. Pore space is largely determined by size and arrangement of aggregates and affects the movement of water, air, and organisms in soil.

- Pore Size Distribution: Macropores ( >75um) Mesopores ( 30-70um) Micropores ( 5-30um) Ultramicropores (0.1-5um) Crytopores ( <0.1um)

- Soil Structure: Aggregation of primary soil particles is a critical determinant of soil structure.Structure is strongly affected by climate, biological activity, density and continuity of surface cover, and soil management practices. Soils that are coarse textured are less likely to have a well-defined structure and therefore fewer structured pore space than s soil high in clay content. Ecological relationships among soil organisms are influenced by soil structure.

Soil Environment

Abiotic factors

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

- 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.

- 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 10 degree increase.

- Toxins poisonous substance produced by living cells or organisms that is active at very low concentrations.

- Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semi-permeable membrane due to a differential in the concentrations of solute.

- 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.

- Bioavailability - Bioavailability is the amount of a contaminant that is absorbed from soil.

Biotic factors

Native vegetation

Microflora

Microfauna

Macrofauna

Anthropogenic (farming, ect.)

References

Edited by students of Kate Scow