The living component includes soil macro- and micro-fauna, and soil microbial communities. They may be active or dormant. The non-living portion of soil organic matter comes from dead macro- and micro-fauna, soil microorganisms, and plant and animal inputs into the soil. These inputs undergo various biological, geological, and chemical processes and are either lost, preserved, or transformed in soil.
Soil organic matter is a complex mixture of plant, animal, or microbial-derived residues at various stages of decomposition. Plants and microbial communities are usually the biggest contributors to soil organic matter. While alive plant roots excrete organic compounds and many plants shed fine roots as they grow. Once dead, plant shoots and roots decay and are transformed in the soil. Microbes make new molecules as they go about their lives. Like other parts of soil, organic matter is dynamic and ever-changing.
Restoring soil fertility via perennialization What soil organic matter contributes to the soil
- Soil organic matter can also interact with soil minerals to form matter that contributes to the formation of soil aggregates. These aggregates are groups of soil particles stuck together with glue-like substances. Root-like hyphae from many fungi function like nets, holding aggregates together. Soil aggregates contribute to soil structure and reduce the potential for soil erosion. Soil aggregation is a strong indicator of healthy soil structure because it reduces stress on root growth and allows for better water infiltration.
- Soil organic matter improves a soil’s ability to hold water. High organic matter increases water infiltration during intense rain events, limiting ponding, and soil saturation. Soil organic matter also can hold water in times of drought.
- Soil organic matter is the most active and dynamic portion of the soil. It is important for regulating many processes related to the global cycling of elements such as carbon.
- Soil organic matter acts as a storehouse and a slow-release fertilizer for many plant nutrients, including nitrogen, phosphorus, and sulphur. It also helps with the exchange of molecules from the water, like dissolved fertilizer and other chemicals. Soil organic matter has a big impact on availability of nutrients that plants can access as they grow.
- Chemical bonds in soil organic matter contain energy, and this energy is consumed by microbes for growth and metabolism. It is this stored energy that drives microbial nutrient cycling and all the other plant-beneficial associations that soil biology maintains with plants.
- Finally, organic matter supports a large and varied faunal and microbial community.
Grounded in Soils is sponsored by the Canadian Society of Soil Science (CSSS) is a non-governmental, non-profit organization for scientists, engineers, technologists, administrators, and students involved in professional soil science.
