Soil organic matter consists of a wide range of organic substances, including living organisms (the soil Biomass). Organic matter is very important to soil function and plant growth as it influences soil structure (and hence aeration, drainage and root growth), water-holding capacity and soil fertility.
Organic matter binds mineral particles into granular or crumb structures (see Soil Structure). It also increases the waterholding capacity of soil, and the proportion that is available for plant uptake. It is a major source of essential plant nutrients including nitrogen, phosphorus, potassium and sulphur. It is also the food for soil organisms, and without it, biochemical activity, which is essential for ecosystem functioning, would cease.