Earthworms are the most important of the soil decomposers and greatly improve soil aggregation. Image credit:pfly Flickr CC BY-SA 2.0
Ladybird beetles, or ladybugs, attack a garden slug. Photo credit: Steve Jurvetson Flickr CC BY 2.0
A soil invertebrate is an invertebrate that spends all or much of its life in the soil. Many soil invertebrates improve the health of the soil and therefore plants; however, some soil invertebrates may be detrimental. Harmful fungi and bacteria may feed on roots and leaves of live plants.
Some nematodes may carry pathogens or parasitize plants and may destroy good soil bacteria. Remedial measures may be taken to promote beneficial organisms, thereby inhibiting the growth of destructive soil organisms.
Soil invertebrates include protozoa, nematodes, worms, mollusks, and arthropods. Members of each of these groupings of invertebrates exhibit characteristics that improve the health of the soil.
The majority of these characteristics fall into the category of increasing soil organic matter and enhancing soil organic matter decomposition.
Benefits of soil organic matter include improvement of soil structure, increases in soil fertility, control of erosion, and increase plant-available water. .