What do soil organisms do?
Growing and reproducing are the primary activities of all living organisms. As individual plants and soil organisms work to survive, they depend on interaction with each other. By-products from growing roots and plant residue feed soil organisms. In turn soil organisms support plant health as they decompose organic matter, cycle nutrients, enhance soil structure, and control the populations of soil organisms, including crop pests.
Organic matter fuels the food web
Soil organic matter is the storehouse for energy and nutrients used by plants and other organisms. Bacteria, fungi, and other soil dwellers transform and release nutrients from organic matter. In general, soil organic matter is made of roughly equal parts of humus and active organic matter. Active organic matter is the portion available to soil organisms. Bacteria tend to use more simple organic compounds, such as root exudates or fresh plant residue. Fungi tend to use more complex compounds, such as fibrous plant residue, wood and soil humus.
Intensive tillage triggers spurts of activity among bacteria and other organisms that consume organic matter (convert it to CO2), depleting the active fraction. Intensive tilling also kill off most if not all of the fungi at will feed on the more complex compounds and humus. The net result is that the active fraction is depleted and there are no fungi to break down the more complex compounds or make the humus available as plant nutrition.
Practices that build soil matter (reduced tillage and regular additions of organic material) will raise the population of active organic matter long before increase in total organic matter can be measured.
Download Microbial life diagram
Typical food web structures
