Recycling of organic wastes for the production of vermicompost and its response in rice-legume cropping system and soil fertility

Investigations were made to recycle agricultural and agro-industrial wastes for the production of vermicompost using earthworms (Eudrilus eugeniae). Its response was studied in a rice-legume cropping system. Different combinations of coirpith/weeds and cowdung/sugarcane pressmud/biodigested slurry were tried for vermicomposting. The study showed that biodigested slurry and weeds was found to be an ideal combination for vermicomposting considering the nutrient content and compost maturity period. The C/N ratio of vermicompost reduced to 12-17:1 from 21-69:1. A pot culture study evaluated the effect of vermicompost in comparison to biodigested slurry and farmyard manure (FYM) on an equal N basis with and without biofertilizer in rice. The study showed that the integrated application of vermicompost, fertilizer N and biofertilizers viz., Azospirillum and phosphobacteria increased rice yield by 15.9%( over application with fertilizer N alone. A field experiment studied the direct and residual effect or different sources of organic N with fertilizer N and biofertilizers in rice -legume crop sequence. The integrated application of 50%,, N through vermicompost, 50%,) via fertilizer N and biofertilizers recorded a grain yield of 6.25 and 0.51 t ha(-1) in the rice and legume, respectively. These yields were 12.2 and 19.9%,) higher than those obtained with 100% fertilizer N alone. On average, integrated application increased the N. P and K uptake by 15.3, 10.7 and 9.4% respectively in rice over fertilizer N alone. Organic carbon content in the residual soil after rice was not depleted due to integrated application. After the legume, organic carbon content increased by 4.55 to 6.82% due to integrated nutrition compared to fertilizer alone. Available N in the residual soil was stable after the rice-legume system. Available P and K contents of the residual soil were depleted considerably in the rice-legume sequence. However, the amount or depletion of available N, P and K in the fertilizer alone treatment was greater than to the integrated nutrition. The microbial population of the residual soil was increased by integrated application. The studies indicate that integrated nutrition comprising vermicompost. fertilizers N and biofertilizers could be applied to rice-legume cropping system to achieve higher yields and sustain soil health. (C) 2001 Elsevier Science B.V. All rights reserved.