Soil Test based Fertilizer Prescriptions under Integrated Plant Nutrient Supply for Rice-Rice Cropping Sequence in Inceptisols of Assam

Abstract

Field experiments were conducted during 2010–12 to assess the fertilizer requirements for rice-rice sequence under integrated plant nutrient supply on Inceptisols (Aeric Endoaquepts) in Jorhat district of Assam. Following Ramamoorthy's Inductive cum targeted yield model, the nutrient requirement per quintal of grain production and contribution from soil, fertilizer and farmyard manure (FYM) were calculated for both autumn and winter rice. The per cent contribution of nutrients from soil (CS), fertilizer (CF) and FYM (CFYM) were found to be 12.49, 45.31 and 32.92 for N, 13.42, 28.52 and 11.84 for P2O5 and 21.99, 47.58 and 29.76 for K2O, respectively for autumn rice. The same for winter rice was 24.60, 33.15 and 48.28 for N, 30.69, 32.15 and 14.38 for P2O5, and 41.00, 56.87 and 31.59 for K2O, respectively. The fertilizer prescription equations were developed and nomograms were formulated based on the equations for a range of soil test values and desired yield target for rice. Under NPK + FYM @ 5.0 t ha−1, 17, 6,14 and 35, 7 and 12 kg ha−1 of fertilizer N, P2O5 and K2O, respectively could be saved for attaining target yield of 40 q ha−1 for autumn rice and 60 q ha−1 for winter rice as compared to NPK fertilizers alone.