Integrated effect of plant density, N rates and irrigation regimes on the biomass production, N content, PAR use efficiencies and water productivity of rice under irrigated semiarid environment

Abstract

Two field experiments were conducted for two years (2000 and 2001) at Agronomic Research Area, University of Agriculture Faisalabad (UAF), Pakistan. There were 15 treatment combinations for experiment-I having three plant densities, viz., one seedling hill-1 (PD1), two seedlings hill-1 (PD2) and three seedlings hill-1 (PD3) and five nitrogen rates, viz., 0, (N0); 50, (N50); 100, (N100); 150, (N150); and 200 (N200) kg N ha-1. Experiment-II also included 15 treatments having three plant densities, viz., one seedling hill-1 (PD1), two seedlings hill-1 (PD2) and three seedlings hill-1 (PD3) and five irrigation regimes, viz., 62.5 cm (I1), 77.5 cm (I2), 92.5 cm (I3), 107.5 cm (I4), and 122.5 cm (I5). A randomized complete block design (RCBD) was employed with three repetitions. The results for experiment-I revealed that the highest biomass (1438 g m-2), grain yield (497 g m-2), crop growth rate (15.36 g m-2 d-1), net assimilation rate (4.24 g m-2 d-1) were observed in the treatment having combination of two seedlings hill-1 and 200 kg N ha-1 (PD2N200). The agronomic and economic nitrogen and PAR use efficiencies were also higher in this treatment. In case of experiment-II, the highest biomass and grain yield were obtained in case of treatment having combination of two seedlings hill-1 and 107.5 cm irrigation regime (PD2I107.5). The irrigation application based water productivity ranged from 0.36 kg mm-3 to 0.61 kg mm-1, irrigation plus precipitation based water productivity ranged from 0.32 kg mm-3 to 0.55 kg mm-3 and evapotranspiration based water productivity ranged from 0.65 kg mm-3 to 0.84 kg mm-3 among 15 treatments combination of plant density and irrigation regimes. This study concludes that for increasing the benefits for the resource-poor growers, the integration of crop management practices is an optimum strategy to substantially increase the resources use efficiency under irrigated semiarid environment.