Effects of supplemental irrigation and nitrogen fertilizer on correlation coefficient and drought tolerance indices of rainfed bread wheat

Determination and identification of effective factors on wheat seed yield under water deficient condition is very important. Nitrogen application causes optimum usage of water and soil resources. In order to study supplemental irrigation and nitrogen fertilizer effect on drought tolerance index and correlation among some physiological traits and grain yield, an experiment was conducted as a split- plot arrangement based on randomized complete block design (RCBD) with three replications during three crop seasons (1999-2002). The treatments were four levels of supplemental irrigation (rainfed, 95, 151 and 207 mm of irrigation) as main plots and five nitrogen rates (0, 30, 60, 90 and 120 Kg N ha-1) as sub plots. The results showed positive and significant correlations of grain yield with biological yield (r=0.96**), plant height (r=0.93**), straw yield (r= 0.92**), seed number per spike (r=0.87**), spike number per square meter (r=0.84**), TKW (r=0.52**) and harvest index (r=0.49**). Path analysis results showed that seed number per spike, plant height, straw and spike number per square meter had main effect on seed yield. Drought tolerance indices of (Tolerance Index, Mean Productivity, Geometric Mean Productivity, Stress Tolerance Index and Harmonic Mean) showed that 95 mm of full irrigation treatment combined with 60 Kg-N ha-1 substantially increased water productivity.