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. …
