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). I ts response was studied in a rice-legume cropping system. Different combina tions of coirpith/weeds and cowdung/sugarcane pressmud/biodigested slurry w ere 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 vermico mpost reduced to 12-17:1 from 21-69:1. A pot culture study evaluated the ef fect of vermicompost in comparison to biodigested slurry and farmyard manur e (FYM) on an equal N basis with and without biofertilizer in rice. The stu dy 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 stu died the direct and residual effect or different sources of organic N with fertilizer N and biofertilizers in rice -legume crop sequence. The integrat ed 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 t hose obtained with 100% fertilizer N alone. On average, integrated applicat ion 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 a fter rice was not depleted due to integrated application. After the legume, organic carbon content increased by 4.55 to 6.82% due to integrated nutrit ion compared to fertilizer alone. Available N in the residual soil was stab le 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 treatme nt was greater than to the integrated nutrition. The microbial population o f the residual soil was increased by integrated application. The studies in dicate 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 r ights reserved.