Beneficial Effects of Soil Organisms [Benefits of Soil Fauna]

Beneficial effects of soil organisms

The soil fauna and flora are indispensable to the plant productivity and the ecological functioning of soils. Of their many beneficial effects, only the most important can be emphasized here. There are several types of soil organisms.

Beneficial effects of soil organisms 

Organic matter decomposition

Perhaps the most significant contribution of the soil fauna and flora to higher plants is that of plant residue decomposition. By this process, dead leaves, roots and other plant tissues are broken down, converting organically held nutrients into mineral forms available for plant uptake. The release of nitrogen is a prime example. Soil organisms also assimilate wastes from animals and other organic materials added to soils. As a by-product of their metabolism, microbes synthesize new compounds, some of which help to stabilize soil structure. Here is another site for the benefits.

Breakdown of toxic compounds

Many organic compounds are toxic to animals and plants. Some of these toxins are produced by soil organisms as metabolic by-products, some are applied purposefully by humans as agrochemicals to kill pests. If these compounds remain unchanged, they would do enormous ecological damage. Fortunately most biologically produced toxins do not remain long in the soil, for soil ecosystems include organisms that not only are unharmed by these compounds but can produce enzymes that allow them to use these toxins as a food.

Toxic compounds in soils

Some toxins are xenobiotic compounds foreign to biological systems, and these may resist attack by commonly occurring microbial enzymes. Soil bacteria ad fungi are especially important in helping maintain a nontoxic soil environment by breaking down toxic compounds. The detoxifying activity of these microorganisms is by far the greatest in the surface layers of the soil, where microbial numbers are concentrated in response to the greater availability of organic matter and oxygen.

Inorganic transformations

The transformation of inorganic compounds is of great significance to the functions of soil systems, including plant growth. Nitrates, sulfates and to a lesser degree, phosphate ions are present in soils primarily due to the action of microorganisms. Bacteria and fungi assimilate some of the N, P and S in the organic materials they digest. Excess amounts of these nutrients may be excreted into the soil solution in inorganic form either by the bacteria and fungi themselves or by the nematodes and protozoa that feed on them.

Nitrogen fixation

The fixation of elemental nitrogen gas, which can not be used directly by higher plants, into compounds usable by plants is one of the most important microbial processes in soils. Actinomycetes is the genus Frankia fix major amounts of nitrogen in forest ecosystems. Cyanobacteria are important in flooded rice paddies, wetlands and deserts and rhizobia bacteria are the most important group for the capture of gaseous nitrogen in agricultural soils.

Rhizobacteria

Some bacteria that live in the rhizosphere damage plants by invading the root cells and living as parasites. Others, called deleterious rhizobacteria, inhibit root growth and function by various non-invasive chemical interactions. These non-parasitic bacteria can cause stunting, wilting, foliar discoloration, nutrient deficiency and even death of affected plants. The build up of deleterious rhizobacteria is warranted in this section on beneficial effects mainly because of their potential as a weed management strategy.

Plant protection

Certain soil organisms attack higher plants but others act to protect plant roots from invasion by soil parasites and pathogens. Also here is the role of soil organisms on soil health. 

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