Compost Quality Prepared from Locally Available Plant Biomass and their Effect on Rice Productivity under Organic Production System

Abstract

Low concentrations of native nutrients in soil, especially nitrogen and phosphorus, are a major constraint limiting crop productivity in highly leached acid soils of the subtropical Indian Himalayas. This is coupled with the negligible use of fertilizers and pesticides, which restricts the productivity of field crops. Further, this area has acute shortage of farmyard manure (FYM) and other organic manures. In a 2-year field study (2004-06) the performance of eight different types of composts prepared from rice straw (Oryza sativa), Eupatorium adhenophorum, Lantana camara, and grass/weed mixtures was evaluated and compared with the recommended combinations of NPK (80:60:40 kg/ha) and FYM on productivity of lowland rice (Oryza sativa L) under organic production. Two composting procedures were evaluated. One was the Microbial Enriched Compost (MEC), procedure consisting of mixing plant biomass and cow dung in equal proportion (weight basis) followed by addition of microbial inoculants in a slurry of fresh cow dung, virgin soil and well rotten compost mixed in a ratio of 1:1: 0.5 along with appropriate amount of water. The second was Microbial and Nutrient Fortified Compost (MNFC) consisting of MEC, 2.5% rock phosphate (w/w) and 1% neem cake. Bioinoculums such as cellulose decomposers (Aspergillus terrus, Trichoderma harzianum, T. viride, T. virens), P-solubilizing microbes (Bacillus polymyxa and Pseudomonas striata) and free-living N-fixers (Azotobacter spp) were used as microbial inoculants to hasten the composting and improve the nutritional quality of the composts. The matured composts had higher NPK contents and lower C/N ratio compared to the fresh dry biomass of the substrates (plant materials used for composting) and FYM. The bacterial population in matured rice straw MNFC compost was about five times higher and fungal and actininomycetes population was about 3 times higher than that recorded with decomposed FYM. The study indicated that the significantly (p = 0.05) higher grain yield was recorded with rice straw MNFC compost in both years (4.50 t/ha in 2005 and 4.68 t/ha in 2006) followed by the Eupatorium MNFC compost (4.33 t/ha and 4.56 t/ha). In general MNFC composts recorded significantly higher grain yields compared to MEC composts indicating superiority of nutritional quality of MNFC composts. The nutrient uptake and post harvest soil fertility status were found to be significantly improved due to application of various composts. Composting with locally available biomass results in higher rice crop productivity and in maintenance of soil health of acid soils of Northeastern region of India.