ABSTRACT
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The vast majority of nutrient cycling processes in soil are carried out by
microorganisms. Organic nutrients and some inorganic compounds are supplied
through animal excreta, death of plants and animals, and exudation by plant roots
of plant-derived photosynthetic material. In agricultural ecosystems, nutrient
input is also provided by fertilizer application. This material must be recycled.
Some nutrients are returned to plants through uptake by roots, while others are
released to groundwaters, to runoff or to atmospheric gases. Although soil
macrofauna (nematodes, worms, enchytraeids) play a role in these recycling
processes, most of them are carried out by soil bacteria, archaea, fungi and
protozoa, for the purpose of this chapter collectively called soil microorganisms.
