Effects Of Water And Fertilizer Reduction And Straw Returning On Crop Yield And Nitrogen And Phosphorus Efficiency Of Wheat-maize System

Proper water and nutrient management are essential to ensure crop yields,efficient use of resources,and environmental safety.However,there are excessive fertilization and irrigation in the wheat-maize rotation system in northern China.Excessive water and fertilizer delay crop maturity,reduce crop yield,increase nutrient leaching,and cause a series of problems such as waste of resources and environmental pollution.Through a 4 year field experiment（2017-2020）,this study explored the effects of water and fertilizer reduction and straw returning on crop yield,nitrogen and phosphorus efficiency and nutrient balance in the wheat-maize rotation system.Five treatments were set up in this experiment,i.e.the farmer’s water and fertilizer inputs（FP）,FP with reduced fertilizer supply（FP-F）,FP with reduced water supply（FP-W）,FP plus straw（FP+S）,FP with reduced both fertilizer and water supplies plus straw（OPT+S）.The main results obtained are as follows:1)Reducing the fertilizer and reducing water did not significantly affect the grain yield and biomass of wheat,maize and wheat/maize system.Straw returning did not affect the grain yield of wheat,increased the grain yield（13.9%,19.1%）and biomass（19.2%,20.0%）of maize in 2018 and 2019.Reducing water and fertilizer combined with straw returning did not significantly affect the grain yield of wheat,but increased the grain yield（11.6%,17.0%）and biomass（20.3%,9.3）of maize in 2018 and 2019.2)Reducing the fertilizer significantly reduced the nitrogen requirement and phosphorus requirement for producing 100 kg wheat grains in 2019-2020（16.8%,10.3%）;reducing the water and fertilizer combined with straw returning significantly increased the nitrogen requirement and phosphorus requirement for producing 100 kg maize grains（19.3%,29.4%）.In 2017,reducing the water and straw returning can significantly increase the phosphorus requirement for producing 100 kilograms of maize by 22.2%.3)Reducing the fertilizer,reducing the water and fertilizer combined with straw returning can significantly improve the partial productivity of nitrogen fertilizer in wheat/maize system by 38.9%and 44.8%,respectively.Reducing the fertilizer can significantly improve the nitrogen absorption efficiency of the three rotation years by an average of 27.4%;the reduction of water and fertilizer combined with straw returning significantly improved the nitrogen absorption efficiency in 2017-2018 and 2018-2019 by an average of 37.2%.In 2019-2020,reducing the fertilizer can significantly improve nitrogen use efficiency by 12.5%.There was no significant difference in nitrogen use efficiency between other years and treatments.4)Reducing the fertilizer,reducing the water and fertilizer combined with straw returning can significantly improve the partial phosphorus fertilizer productivity in wheat/maize system by 38.1%and 43.9%,respectively.Reducing the fertilizer,reducing the water and fertilize combined with straw returning can significantly improve the phosphorus absorption efficiency by 35.5%and 38.6%In addition,there was no significant difference in phosphorus utilization efficiency among treatments.5)All five treatments showed a surplus of nitrogen and phosphorus,among which the nitrogen surplus in the straw plus farmer’s water and fertilizer inputs was the highest(440kg·ha^-1·yr^-1),the nitrogen surplus was the lowest under reducing fertilizer(156 kg·ha^-1·yr^-1).Similarly,the treatment of straw plus farmer’s water and fertilizer inputs also had the highest phosphorus surplus(86.4 kg·ha^-1·yr^-1),the phosphorus surplus was the lowest under reducing fertilizer(50.2 kg·ha^-1·yr^-1).To sum up,reducing fertilizer did not reduce the crop yield,at the same time improved the partial productivity of nitrogen and phosphorus fertilizers and the absorption efficiency of nitrogen and phosphorus,and also reduced the surplus of nitrogen and phosphorus in the soil.Reducing water had no effect on crop yield and nitrogen and phosphorus efficiency.Straw plus farmer’s water and fertilizer inputs tended to increase corn yield,but it increased the surplus of nitrogen and phosphorus.The reduction of water and fertilizer plus straw also tended to increase the yield of corn,and at the same time,it improved the partial productivity of nitrogen and phosphorus fertilizers and the absorption efficiency of nitrogen and phosphorus.Therefore,reducing the amount of water and fertilizer plus straw returning could achieve the goal of high yield,high efficiency and environmental friendliness.