Vermicompost Biofertilizers

Abstract

Role of vermicompost in nourishing agricultural crops has attracted the attention of researchers throughout the globe in past few decades. Vermicompost is the method of using earthworms to transform organic waste into nutrient rich compost. The earthworms’ casting is nutritive organic manure rich in humus, NPK, micronutrients, beneficial microbes, antibiotics, enzymes, growth hormones, etc. There are many reports in literature showing beneficial effects of imbedding vermicompost in soil. Application of vermicompost as organic manure in soil built-up organic carbon, improve nutrient status, enhance cation exchange capacity, microbial activities, microbial biomass carbon and enzymatic activities. The earthworms’ castings also have pest repellent attributes. Beside that vermicompost also improves soil structure, soil aggregation and improve water retention capacity.

Introduction
The use of chemical fertilizers has increased tremendously from green revolution leading to heavy dependence on chemical fertilizer in conventional agricultural system. The application of chemical fertilizers, no doubt has increased the crop productivity many folds, but their continuous and imbalanced application has also produced detrimental effects on soil health due to which crop yields have become stagnated in past few decades. The long term fertilizer experimental studies indicated that continuous sole application of chemical fertilizer in imbalanced manner produce detrimental effects on soil physical, chemical and biological properties further, inducing secondary and micronutrient deficiencies in soil, nutrient imbalance in soil and plants, environmental hazards and decrease in total factor productivity. Microbial population in soil also severely affected due to imbalanced fertilizer application. Moreover, excessive fertilizer applications are also contaminating surface and underground water bodies especially by nitrate leaching (Pimentel, 1996) and causing detrimental effects on environment, which in turn is causing serious hazards to human and animal health. Therefore, in present context, there is dire need to follow climate resilient integrated crop management modules so that soil health and crop productivity could be sustained for longer time. In above scenario, one of the possible options to reduce the use of chemical fertilizer could be recycling of organic wastes. Thus, inclusion of vermicompost organic manure in crop production is a better alternative for improving soil health, crop productivity and quality as it exert a significant positive influence on soil properties and microbial population. Vermicompost is the method of using earthworms to transform organic waste into nutrient rich compost. Soil earthworms play an important role in agriculture, it decomposes dead organic litter by consuming them and release as castings. The earthworms accelerate decomposition of plant litter and organic matter and improve soil fertility by releasing mineral elements in the forms that are easily
uptake by plants (Curry, 1987). Vermicompost contains most nutrients in plant available form such as nitrates, phosphates, exchangeable calcium and soluble potassium (Edwards, 1998; Orozco, 1996). The behavioural activity of earthworms that is feeding, burrowing and casting, modify the physical, chemical and biological properties of organic matter and soil for plant growth and nutrient acquisition. Due to large surface area, vermicompost offers several micro sites for nutrient retention and exchange and microbial activity (Shi-wei and Fu-Zhen, 1991). Vermicompost is usually rich in microbial populations and diversity particularly fungi, bacteria and actinomycetes

Earthworms and raw material for vermicomposting

There are more than 3000 species of earthworms in the soil (Cook and Linden,
1996), but hardly 8-10 species are found suitable for vermicompost preparation. The best types of earthworms for vermiculture and vermicomposting are epigaeic species (litter dwellers, live in organic horizon) such as Eisenia fetida and Eudrilus eugeniae (Bansal and Kapoor, 2000; Dominguez and Edwards, 2004). These worm species like to settle on top soil and prefer to eat organic scraps such as vegetable waste, compost and organic bedding and produce richer casting than those that feed on plain soil. These worms have been recognized as the worm species that can eat as much as half of its weight on a daily basis. They work efficiently in breaking down and decaying natural remains and turning these scraps into high-quality organic compost. Further, above species of earthworms are resistant to temperature and moisture fluctuations. Moreover, these species multiply rapidly and remain active throughout the year, decompose organic material rapidly (rapid casting) and help to prepare vermicompost in shorter duration. Other species of red worms or red wigglers such as Lumbricus rubellus, Perionyx sansibaricus, Perionyx excavatus, Eisenia andreii, etc. could also be successfully used in vermicompost production (Dominguez andEdwards, 2004). Cattle dung or farm yard manure (FYM) is used as raw material for vermicomposting, beside that any material that can be decomposed easily such as weeds, wastes (leaves and rind) of vegetables and fruits, crop residue, roughage of the animals as well as municipal wastes of organic origin could also be utilized for vermicompost preparation (Alves and Passom, 1997; Atiyeh et al., 1999; Kamergam et al., 1999; Kiehl, 2001). The organic waste consumed by earthworms undergo physical breakdown in the gizzard, which is then exposed to various enzymes such as protease, cellulose, lipase, chitinase, amylase, etc. secreted into lumen by the gut wall and associated microbes. Above enzymes causes breakdown of complex biomolecules into simple ones. Mucus secretions of gut wall provide structural stability of vermicompost. Only 5-10% of the ingested material is absorbed by earthworms for their growth and remaining is excreted as casting.