Particulate organic matter

Particulate organic matter (POM, macroorganic matter, or coarse fraction organic matter) is defined as soil organic matter between 0.053 mm and 2 mm in size. Isolated by sieving, this fraction includes partially decomposed soil detritus and plant material, pollen, and other materials. Consistent sieving is important when determining POM content because isolated size fractions will depend on the force of agitation

POM is readily decomposable and serves many soil functions. It is a source of food or energy for soil organisms and nutrients for plants. POM also enhances soil structure leading to increased water infiltration, aeration and resistance to erosion Soil management practices, such as tillage and compost/manure application, alter the POM content of soil and water.

The decomposition of POM provides energy and nutrients. Nutrients not taken up by soil organisms may be available for plant uptake. The amount of nutrients released (mineralized) during decomposition depends on the biological and chemical characteristics of the POM, such as the C:N ratio. In addition to nutrient release, decomposers colonizing POM play a role in improving soil structure. Fungal mycelium entangle soil particles and release sticky, cement-like, polysaccharides into the soil; ultimately forming soil aggregates

Soil POM content is affected by organic inputs and the activity of soil decomposers. The addition of organic materials, such as manure or crop residues, typically results in an increase in POM. Alternatively, repeated tillage or soil disturbance increases the rate of decomposition by exposing soil organisms to oxygen and organic substrates; ultimately, depleting POM. Reduction in POM content is observed when native grasslands are converted to agricultural land. Soil temperature and moisture also affect the rate of POM decomposition. Because POM is a readily available (labile) source of soil nutrients, is a contributor to soil structure, and is highly sensitive to soil management, it is frequently used as an indicator to measure soil quality.

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