If you are keen to dive deeper into this topic, have a look at the brochure Farming with Soil Life published by the Xerces Society for Invertebrate Conservation.
The number and diversity of living organisms in soil are considered important indicators of soil health. There are various ways in which soil life can be examined. You can test overall soil ‘aliveness’ through the ‘tea bag’ decomposition test, or a soil respiration measurement. Within a soil, observations such as organic matter, root channels, cavities, or tunnels can provide hints on how well the soil functions as a habitat. You can also deduce the level of soil biological activity from testing field aggregate stability or lab results such as soil microbial biomass and hot water extractable carbon.
More specialists examinations of particular soil animal groups can provide insight into status of biological soil health. Examples are pitfall traps to study litter-decomposing invertebrates at or near the soil surface; or the measurement of earthworm abundance and diversity.
