Role of Earthworms in Soil Fertility and Factors Affecting their Population Dynamics: A Review

Earthworms mix soil layers and incorporate organic matter into the soil. This mixing allows the dispersion of the organic matter through the soil and makes the nutrients held in it available to plants and improves the fertility of the soil. Earthworms when present improve the soil physical, chemical and biological properties and acts as soil conditioner. They do so by fragmentation, aeration, breakdown of organic matter in soil and release plant available nutrients and also due to secretion of plant growth hormones, their role in nitrogen fixation, carbon dynamics, and phosphorous dynamics. But their population in soil is threatened by a number of soil and environmental factors. Agricultural practices like heavy tillage operation and application of chemical fertilizers also contribute in the reduction of earthworms in soil. Change in land use due to increase in human population brings change in the system and make it unsuitable for the growth and development of earthworms. This review was thus made to understand the factors that affect the population dynamics of earthworms in any system so that appropriate environmental condition and earthworm friendly agricultural practices can be adopted for optimum activity of earthworms and for fertile and productive soil.