Effect of nitrogen and phosphorus rate on use efficiency of soil water and interaction of water and fertilizer in dryland spring wheat

Based on a long-term experiment and a pot experiment,the interaction effect of water and fertilizer and effect of nitrogen and phosphorus rate on change of soil water,valid water utilization,water consumption and saving,evaporation and water use efficiency were studied in dryland spring wheat.The results indicated that interaction of water and fertilizer on yield increasing was significant in pot experiment,and the use efficiency of fertilizer and soil water was increased by 28.6% and 124%,respectively.Yield compensation benefit of soil water and fertilizer utilization per unit was 471.5∶7.0,that is to say,the change limit of soil water and fertilizer for main effect was 17.4%.The maximum income was 4 970.0 yuan/hm2 with a fertilization rate of 247.4 kg/hm2(N∶P2O5=1∶0.75) and soil water of 19.7%.Nitrogen and phosphorus rate increased soil valid water utilization of 0～200 cm soil depth from 44.9% to 54.2% after spring wheat was harvested.Compared to CK,the evaporation of treatment N60P45、N120P90 and N180P135 was increased by 22.7, 38.0 and 47.8 mm,the ratio of transpiration and evaporation increased by 0.04,0.07 and 0.08,respectively.And the efficiency of grain transpiration increased by 0.08,0.24 and 0.14 g/kg compared to CK,respectively.Nitrogen and phosphorus fertilization together could raise soil valid water utilization rate,evaporation rate and water use efficiency of spring wheat,and improve the grain yield of crops.Therefore,rational nitrogen and phosphorus rate in the field is an important way to raise water use efficiency of crop and hence agriculture production.