Effect of Plant Competition on Water Use Efficiency of Intercropping Fenugreek and Nigella under Different Moisture Regimes

Increasing water use efficiency (WUE) is one of the most important strategies for mitigating water deficiency crisis. The aim of this study was to investigate the effect of plant competition on water use efficiency of intercropping under different moisture regimes. The experiment was a split–split-plot design with three replications. The main plot consisted of three levels of soil moisture including W1: full irrigation, W2: mild stress (irrigation on the basis of 75% W1), W3: severe stress (irrigation on the basis of 75 % W1). The subplot contained five planting patterns: fenugreek sole crop, nigella sole crop and three mixed ratios (2:1, 1:1, 1:2 of fenugreek and nigella). Results showed that the greatest WUE for seed production (WUEs) was obtained in fenugreek: nigella (1:2) treatment under drought stress conditions. Under mild stress conditions, the WUEs in fenugreek: nigella (1:2) treatment was even higher than nigella sole crop under no stress conditions, under which the highest WUE for biomass was observed in fenugreek: nigella (1:2) and (2:1) treatments and the lowest level was in nigella sole crop. The water equivalent ratio (WER) of intercropping treatments was superior to each of the sole crops of fenugreek and nigella. Under mild stress conditions, the maximum level of WER in fenugreek: nigella (1:2) and (2:1) treatments was 1.44 and 1.47, respectively. It can be concluded that interspecies competition is one of important strategies to increase the WUE and production under drought stress conditions.