Role of earthworms in soil fertility and its impact on agriculture: A review

Soil fertility is defined as the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. Perhaps no other living organism in the soil is as important as an earthworm in helping to increase soil health. Earthworms are the most commonly occur in the soil. The activities of burrowing and feeding by earthworms have many valuable effects generally on soil quality for crop production. Earthworms increase soil aeration, infiltration, structure, nutrient cycling, water movement, and plant growth. Earthworms are one of the major decomposers of organic matter. They get their nutrition from microorganisms that live on organic matter and in soil material. When they move through the soil eating, earthworms form tubular channels or burrows. These burrows can persist for a long time in the soil. Earthworm burrows increase soil porosity which increases the amount of air and water that get into the soil. Increased porosity also lowers bulk density and increases root development. Earthworm excrement or casts increase soil fertility because it contains nitrogen, phosphorus, potassium, and magnesium. Earthworm casts also contain microorganisms which increase in abundance as organic matter is digested in their intestines. The cycling of nutrients from organic matter and the increase in microorganisms facilitates plant growth. They cast along with binding agents released by earthworms also improve soil structure and increase aggregate stability. The soil biota benefits soil productivity and contributes to the sustainable function of all ecosystems. The cycling of nutrients is a critical function that is essential to life on earth. Earthworms (EWs) are a major component of soil fauna communities in most ecosystems and comprise a large proportion of macrofauna biomass. Their activity is beneficial because it can enhance soil nutrient cycling through the rapid incorporation of detritus into mineral soils. In addition to this mixing effect, mucus production associated with water excretion in earthworm guts also enhances the activity of other beneficial soil microorganisms. This is followed by the production of organic matter. So, in the short term, a more significant effect is the concentration of large quantities of nutrients (N, P, K, and Ca) that are easily assimilable by plants in fresh cast depositions. In addition, earthworms seem to accelerate the mineralization as well as the turnover of soil organic matter. Earthworms are known also to increase nitrogen mineralization, through direct and indirect effects on the microbial community. The increased transfer of organic C and N into soil aggregates indicates the potential for earthworms to facilitate soil organic matter stabilization and accumulation in agricultural systems, and that their influence depends greatly on differences in land management practices.