Resources use efficiency of field grown transplanted rice (Oryza sativa L.) under irrigated semiarid environment.

Abstract

Resources use efficiency of rice crop was studied under irrigated semiarid conditions. Two field experiments were conducted at the Experimental Farm, University of Agriculture, Faisalabad (UAF), Pakistan (latitude 31o25´N, longitude 73o09´E, and altitude 184.4 m from sea level), for two years. Variables in the study include viz. three population densities, five nitrogen fertilizer rates in the first experiment and similarly three population densities and five irrigation regimes in the second experiment. For these resources, radiation interception and radiation conversion efficiency (RCE = ), water use and water use efficiency (WUE = w), agronomic nitrogen use efficiency (ANUE = an) and economic nitrogen use efficiency (ENUE = en) were estimated. Relationships were also studied among various resources. Particularly RCE () and WUE (w) were estimated by two approaches. The results revealed in experiment that cumulative intercepted photosynthetically active radiation (CIPAR) varied from 990 to 1016 MJ m -2 in various nitrogen fertilizer levels. Plant density did not affect significantly RCE in both the seasons and it ranged from 1.26 to 1.28 g MJ-1 among different densities. Averaged over the two years data mean RCE for cumulative above-ground total dry matter (CATDM) ranged from 1.15 to 1.36 g MJ -1 among different fertilizer levels. The results depicted in Experiment 2 revealed that increasing density from one seedling hill -1 to three seedlings hill -1 significantly increased the CIPAR. Averaged over the two years data of RCE ranged from 1.41 to 1.44 g MJ -1 . Increasing application of irrigation significantly and linearly enhanced RCE for CATDM ranging from 1.34 to 1.49 g MJ -1 . Overall cumulative crop evapotranspiration (CCET) varied from 540 to 575 mm among different densities. Similarly CCET varied from 464 to 632 mm among different irrigation regimes. WUE varied from 23.1 to 23.7 kg ha -1 mm -1 among different densities. Averaged over the two seasons WUE for CATDM decreased with increasing application of irrigation and ranged from 25.2 to 21.9 kg ha-1 mm-1. The relationships between CATDM production and cumulative leaf area duration (CLAD) and CIPAR in Experiment 1 and CLAD, CIPAR and CCET in Experiment 2 were linear. Agronomic and economic nitrogen use efficiencies were higher at NF3 (N 150 kg ha -1 ).