THE IMPORTANCE OF SOIL ORGANISMS

The cycling of chemical element and transfer of energy in ecosystems cannot operate efficiently without the presence of a wide variety of soil organisms. The importance of the soil organisms can therefore not be overemphasized. Microorganisms, for example, mammals -rats,mice,rabbits etc. contribute to large scale turnover and aeration of the soil.

Nematodes which are free living are usually present in large numbers (10 to 20 minion/m) in the soil. they have a similar role to earthworms although saprophytic and parasitic forms also exist. The Microorganisms are represented by the protozoa, bacteria, fungi, actinomycetes, algae and viruses. Protozoa usually prey on bacteria and some fungi although they may also be saprophytic. Protozoa present in the soil include rhizopods or amoeba, and the free swimming flagellates and ciliates. Bacteria are the most numerous and may occur in densities up to 10 per g. The activities of soil organisms are rife in the weathered horizons of many soils, particularly close to plant roots or the rhizosphere. A complex situation arises when soil enzymes are absorbed into clay particles which cause considerable modification not only of some specific relationship among the fauna, but also of chemical exchanges within the soil.

Earthworms are important in turning over soil particles and at the same time taking in fresh organic material and releasing nutrients in a form readily available to plant intake.