Effect of plant residue and fertilizer on grain yield of dryland rice under reduced tillage cultivation

Abstract

Use of reduced tillage practices and inputs of organic materials, rather than chemical fertilizers, has been suggested as a method of ‘low input agriculture’ to achieve sustainability in dryland agriculture. This study evaluated the effects of incorporation of plant residue and chemical fertilizer under reduced tillage on biomass and grain yield of dryland (rainfed) rice ( Oryza sativa L.). Four treatments were established: (a) a no-input control; (b) chemical fertilizer 80 kg N ha −1, 40 kg P ha −1, and 30 kg K ha −1; (c) air-dried wheat straw (organic C 378 g kg −1, total N 4.8 g kg −1, total P 0.9 g kg −1, C/N ratio 75.5) at 20 Mg ha −1 (the amount of N in straw was equivalent to that applied with chemical fertilizer); (d) wheat straw + fertilizer, straw applied at 10 Mg ha −1 and rate of fertilizer 50% of (b). The soil type at the site is a Inceptisol and, a silt loam, pH 6.7 and water holding capacity 405 g kg −1. Straw and fertilizer treatments were applied about 3 weeks before planting. Inorganic N (nitrate + ammonium-N) concentrations in the control, fertilizer, straw, and straw + fertilizer amended soils were 7.2, 11.6, 8.6 and 11.5 μg g −1, respectively. Available P was greatest in the straw + fertilizer treated plots (16.7 μg g −1) followed by fertilizer (16.0 μg g −1), straw (14.2 μg g −1) and the control (12.0 μg g −1). The rates of N-mineralization in the straw + fertilizer, fertilizer and straw treatments were 16.6, 14.3 and 11.2 μg g −1 month −1, respectively. Microbial biomass C, N and P were 66, 77 and 49% greater, respectively, in the straw + fertilizer treated plots than in the control. Total crop biomass ranged from 6.79–9.91 Mg ha −1 and grain yield ranged from 1.08–1.46 Mg ha −1, both in the order: control < straw < fertilizer < fertilizer + straw. There were strong positive relationships between grain yield and microbial biomass ( r= 0.84, P < 0.001), N-mineralization ( r=0.85, P < 0.001), and available P ( r=0.84, P < 0.001). The combined input of straw and fertilizer could be an ideal practice to improve soil fertility and thereby the productivity of rice under dryland (rainfed) conditions.