85 Indian Journal of Agricultural Sciences 82 (1): 85–8, January 2012 Optimizing crop residue-based composts for enhancing soil fertility and crop yield of rice* S K DADHICH 1 , A K PANDEY 2 , R PRASANNA 3 , L NAIN 4 and B D KAUSHIK 5 Indian Agricultural Research institute, New Delhi 110 012 Received: 20 August 2010; Revised accepted: 15 October 2011 Key words: Composts, Microbiological activity, Nutrient availability, Organic carbon, Rice crop Effective waste management, especially of crop-based residues has become an issue of immense significance in agriculture since the harmful effects of chemical inputs in agriculture are looming large over the environment. In this context, recycling of crop residues and organic wastes through composting represents the key technology for the production of organic manures and their use as nutrient supplements in soil to replace the chemical fertilizers. As per FAO “Organic agriculture is a unique production management system which promotes and enhances agro- ecosystem health, including biodiversity, biological cycles and soil microbial activity and this is accomplished by using on-farm agronomic, biological and mechanical methods in exclusion of all synthetic off-farm inputs”. The utilization of crop residues to prepare composts and their application in nutrient management of crops is one such option. Compost provides a stable organic product that improves the physical, chemical and biological properties of soils, thereby enhancing soil quality and crop production (Gaind and Nain 2010). When compost is applied correctly, several beneficial effects on soil properties are recorded, including creation of suitable conditions for root development leading to higher yields and improved quality of crops (Lata et al. 2005, Gaind et al. 2006, Pandey et al. 2009). The role of organic matter or carbon in agriculture is well known and composts are known to improve soil structure and humus content as well as supply macro and micronutrients (Vasanthi and Kumaraswamy 2000).Most of the earlier work has been focused on cereal residue-based compost prepared by natural method of composting. The present investigation was undertaken with composts prepared by the improved method of composting using inoculum of efficient microorganisms (Lata et al. 2005) using legume crops (chickpea, pigeonpea stover) and mustard stover, on which very scanty information is available. The effect of these bioaugmented composts was compared with recommended chemical fertilizers on productivity of rice and selected soil microbiological parameters in a field experiment. A field experiment was carried out at the experimental farm of Indian Agricultural Research Institute; New Delhi during rainy (kharif) season of 2007 to evaluate the effect of three composts prepared using pigeonpea stover, chickpea stover and mustard stover. These crop wastes were composted in the pits for 60 days using inoculation of selected bacteria, fungus and actinomycetes (Lata et al. 2005) with mustard cake amendment to lower the C:N ratio to 50:1. These composts were analyzed for total carbon; N and humus content (Hesse 1971) as given in Table 1. The experiment was laid out in randomized block design with four replications and treatments including: T 1 -N 120 P 60; T 2 -N 60 P 30 ;T 3 -pigeonpea stover compost @5tonnes/ha; T 4 -chick pea stover compost @ 5tonnes/ha; T 5 - mustard stover compost) @ 5tonnes/ ha.Nitrogen was applied through urea and P (P 2 O 5 ) through single super phosphate at the time of transplanting rice (var. Pusa Basmati1) as per treatments. Composts were applied before 20 d of transplanting rice in field. The row-to-row and * Short note *Based on Post Doctoral work of first author 1 Assistant Professor (Soil Science) (e mail: drskd2001@ yahoo.com), Krishi Vigyan Kendra (MPUA&T, Udaipur), Sirohi 307 001; 2 Senior Research Fellow (e mail: alok2k2@gmail.com) 3 Senior Scientist (e mail: radhpr@gmail.com), 4 Principal Scientist (e mail: latambio@yahoo.com), Division of Microbiology; 5 Professor (Biotechnology) (e mail: bd.kaushik@aecsgi.org) Table 1 Characteristics of the composts Compost C N C/N Humus (%) (%) (%) Pigeonpea stover compost 23.78 1.28 18.57 11.36 Chickpea stover compost 27.26 1.25 21.80 11.14 Mustard stover compost 24.26 1.22 19.80 10.82