What types of organism are found in the soil?

Traditionally soil organisms have been divided into 3 size class ranges.

Some fungi groups play an important role in the decomposition of woody tissue, which is difficult to decompose because of its high lignin concentration. The majority of nematodes feed upon members of the microbiota, helping to recycle nutrients.

In terms of nutrient cycling and beneficial effects on soil structure, earthworms are probably the most important members of the macrobiota. Earthworms tend to be greatest in neutral soils (pH 7), that have high concentrations of organic matter. They play a crucial role in the physical breakdown of organic matter into smaller units, thereby increasing its surface area and speeding up its decomposition by soil bacteria and fungi.

The following shows the size differences of soil organisms:-

and the following shows the approximate numbers of organisms (per gram) commonly found in the microbiota:-