Functions of Humus
1. Effective humus and stable humus are further sources of nutrients to microbes, the former provides a readily available supply, and the latter acts as a longerterm storage reservoir.
2. Humus is a colloidal substance and increases the soil’s cation exchange capacity. From 20 to 70% of the exchange capacity of the soil is owing to colloidal humic substances.
3. Humus can hold the equivalent of 80–90% of its weight in moisture and therefore increases the soil’s capacity to with stand drought conditions.
4. The dark color of humus (usually black or dark brown) helps to warm up cold soils in the spring.
5. Humus has a profound effect on the structure of soils. The deterioration of structure that accompanies intensive tillage is usually less severe in soils adequately supplied with humus.
6. Humus definitely increases the ability of the soil to resist erosion. It enables the soil to hold more water.
7. Humus serves as a source of energy for both macro and microorganisms. The numbers of bacteria, actinomycetes and fungi in the soil are related in a general way to humus content; Faunal organisms are similarly affected.
8. The biochemical structure of humus enables it to moderate or buffer excessive acid or alkaline soil conditions.
9. Organic substances in soil have a direct physiological effect on plant growth. Some compounds such as phenolic acids have photo toxic properties; Others such as the auxin, enhance the growth of higher plant.
10. Humus modifies the normal process of rock weathering by increasing the rate of dissolution of rock material. The productivity of present day soils is intimately related to the effect that humus has no profile development.