Effect of fertilizer nitrogen and varied C:N ratio of mushroom compost on rice yield and nitrogen forms of soil

Field experiment was conducted to evaluate effect of spent mushroom composts of varied C:N ratio with and without fertilizer nitrogen on yield, nitrogen uptake and nitrogen forms in rice grown on the Inceptisol of Allahabad. Nitrogen mineralization from oyster spent mushroom compost (OYSMC) was slower than from white button spent mushroom compost (WBSMC) when used alone or with mineral fertilizer nitrogen. Ammonia nitrogen dominated over nitrate nitrogen among mineral nitrogen forms. The highest accumulation of nitrate and ammonia nitrogen occurred under conjunctive use of narrow C:N ratio WBSMC with mineral fertilizer nitrogen. Hydrolysable nitrogen content generally decreased with use of mineral fertilizer nitrogen, compared to varied C:N ratio composts. An increase in the organic nitrogen forms, i.e. nitrogen contained in amino sugars, amino acids and ammonia nitrogen was conditioned primarily on the application of composts. Crop yield was even lower than control when wider C:N ratio OYSMC was used but highest yield was obtained by supplying nitrogen through WBSMC and mineral fertilizer nitrogen. Application of WBSMC 5 t ha -1 can produce a rice yield comparable with that produced from application of fertilizer nitrogen 90 kg ha -1