Effects of nitrogen rates and irrigation rates on grain yield and water use efficiency of spring wheat on recently reclaimed sandy farmland in Heihe River basin

Every year, increasing newly reclaimed sandy farmlands are irrigated for planting crops in Heihe River basin, however, the high irrigation and high nitrogen(N) supply are major factors contributing to water quantity and shortage problems in this area. The study was conducted at Linze Inland River Basin Research Station(CERN) to establish an accurate irrigation and N management system for spring wheat production aimed at high yield, water use efficiency(WUE) and economic return, by using a randomized complete block split plot design, with irrigation regimes［0.6, 0.8, 1.0 of the estimated evapotranspiration(ET)］ and N fertility rates［79, 140, 221, 300 kg/hm²］ as the main-plot and split-plot respectively. Irrigation and N had significant effects on yield, yield components and WUE. Grain yield and yield components increased linearly in response to irrigation in all N treatments, the average reductions in grain yield, kernel weight and number of kernels were 21.98%, 14.68% and 9.10% with 0.6 ET relative to 1.0 ET, respectively. The 0.6 ET had a significantly higher WUE than 0.8 ET and 1.0 ET, the difference of WUE was not significant between 0.8 ET and 1.0 ET in all N treatments. Grain yield and yield components were the greatest at N rate of 221 kg/hm² treatment among other N treatments in all irrigation regimes. This study showed that the most profitable N rates ranged from 226.8 kg/hm² to 227.9 kg/hm² were less than maximum N rates ranged from 277.4 kg/hm² to 305.1 kg/hm² related to 0.6 ET and 1.0 ET. It indicates optimizing irrigation and N supply can produce maximized profits and high WUE for spring wheat production on newly reclaimed sandy farmlands in Heihe River basin. Irrigation treatment 0.6 ET, accompanied by N rate of 221 kg/hm² was the best management system for the relative high economic yield and high WUE.