Organic Matter and Factor Affecting Organic Matter in Soil

Organic Matter

Soil organic matter is composed of decomposing residues (plants and animals), by-product formed by decomposition, microorganisms and materials resistant to further decomposition. Generally, a mineral soil contains 2-5 %organic matter. Organic matter plays a variety of roles in nutrient, water and biological cycles in soil system.
Source of organic matter: common organic waste materials which could be used to increase soil organic matter include animal manures, crop residues, composts, green manure, sewage sludge, food processing wastes, industrial organic wastes, wood manufacturing wastes and municipal wastes.

Factor Affecting Organic Matter in Soil

The amount of organic matter in soil is the result of two processes: the addition of organic matter and the loss of organic matter through decomposition. The following four factors affect both addition and losses.
Management
                Practices that increase plant growth on a field (cover crops, irrigation, etc.) will increase the amount of roots and residues added to the soil each year. On the other hand, intensive tillage decrease organic matter by speeding up decomposition.
Soil texture
                Fine-textured soils can hold much more organic matter than sandy soils. Decomposition occurs faster in well aerated sandy soils. A sandy loam rarely holds more than 2 % organic matter.
Climate
                High temperature speeds up the degradation of organic matter. In areas of high precipitation there is more plant growth and therefore more roots and residues are added to the soil as source of organic matter.
Vegetation

                In grasslands, organic matter is added to the soil each year from grass roots that extend deep into the soil. In forests, the organic matter comes from leaves that are dropped on the surface of the soil. 

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