Soil organic matter

Soil organic matter SOM is the organic matter component of soil , consisting of plant and animal detritus at various stages of decomposition , cells and tissues of soil microbes , and substances that soil microbes synthesize. SOM provides numerous benefits to soil's physical and chemical properties and its capacity to provide regulatory ecosystem services.

The benefits of SOM result from several complex, interactive, edaphic factors; a non-exhaustive list of these benefits to soil function includes improvement of soil structure , aggregation , water retention , soil biodiversity , absorption and retention of pollutants , buffering capacity , and the cycling and storage of plant nutrients.

SOM increases soil fertility by providing cation exchange sites and being a reserve of plant nutrients , especially nitrogen N , phosphorus P , and sulfur S , along with micronutrients , which the mineralization of SOM slowly releases. As such, the amount of SOM and soil fertility are significantly correlated.

Organic matter in soil is also called

SOM also acts as a major sink and source of soil carbon C. Soil represents one of the largest C sinks on Earth and is significant in the global carbon cycle and, therefore, for climate change mitigation. SOM can be divided into three genera: the living biomass of microbes , fresh and partially decomposed detritus, and humus. Surface plant litter , i.

The primary source of SOM is vegetal detritus. In forests and prairies , for example, different organisms decompose the fresh detritus into simpler compounds.