Optimal Supply of Water and Nitrogen Improves Grain Yield, Water Use Efficiency and Crop Nitrogen Recovery in Wheat

Little information is available on the role of optimized application of irrigation and N on crop N recovery and NO3-N build up and movement in soil profile.A field experiment was carried out to evaluate the effects of irrigation and N management practices on wheat yield, water and fertilizer use efficiency and NO3-N distribution in soil.The treatments included were three levels of irrigation; 0.7, 1.0 and 1.3% of the estimated evapo-transpiration (ETc) and four levels of N; 0, 110, 160 and 210 kg N ha -1 in split plot design.The N was applied either in two splits (50% at sowing + 50% at maximum tillering) or three splits (50% at sowing + 25% at maximum tillering + 25% at spike initiation).Nitrogen applied at 110 kg ha -1 in three splits produced higher wheat yield, N recovery and water use efficiency (WUE) than two splits.Further, application of N in three splits had considerably lesser accumulation of NO3-N in soil as compared to two splits.A significant irrigation effect was observed on grain yield, N recovery and WUE.The highest levels were achieved with water application according to crop water requirement (1.0 ETc).The deficit irrigation produced significantly lower grain yield (3.15 t ha -1 ) than full (3.80 t ha -1 ) and excessive (3.80 t ha -1 ) irrigations.Response of WUE to irrigation levels was in the order, 1.0 ETc (11.03 kg ha -1 mm -1 )>0.7 ETc (10.63 kg ha -1 mm -1 )>1.7 ETc (9.84 kg ha -1 mm -1 ).Deficit irrigation resulted in higher build up of NO3-N in surface soil.In contrast, excessive irrigation resulted in greater concentration of NO3-N in lower depths of soil.The results from this research show that there is great potential for decreasing N leaching and increasing wheat crop yield and N use efficiency thorugh controlled irrigation and N application according to crop demand.