Effects Of Water And Fertilizer Optimization On Nitrogen And Phosphorus Leaching Loss In Wheat-maize Rotation System

In order to efficient utilization of nitrogen and phosphorus resources and reduce or prevent it leaching losses in wheat-maize rotation system in cinnamon soil region,the present study was to explore the effect of water and fertilizer optimization,straw returning and biochar application on yield,nitrogen and phosphorus use efficiency and nitrogen and phosphorus leaching loss in wheat-maize rotation system by means of lysimeter experiments.The present study involved eight treatments,i.e.farmer practice?FP1,FP2?,less water supply under FP1?FP1-W?,less fertilizer supply under FP1?FP1-F?,biochar application under FP2?FP2+BC?,water and fertilizer optimization?OPT?,straw returning plus OPT?OPT+S?,biochar application plus OPT?OPT+BC?.The main results obtained were as follows:1)Compared with FP1,FP1-W or FP1-F had no significant effect on grain yield and aboveground biomass of wheat/maize.Compared with FP1,OPT treatment did not reduce wheat grain yield but it reduced maize grain yield by 26.1%in the first year,and reduced wheat grain yield by 14.8%in the second year.FP2+BC did not affect grain yield of wheat/maize in the first year,but increased the maize yield in the second year compared with FP2 treatment.Both OPT+S and OPT+BC did not affect wheat/maize yield for two years.2)Compared with FP1,the FP1-F treatment increased partial factor productivity of nitrogen and phosphorus by 35.5%and 71.2%,respectively,the efficiency of nitrogen and phosphorus?balance method?by 30.4%and 95.3%,respectively.OPT also increased the partial factor productivity of nitrogen and phosphorus by 23.6%and 55.8%,and nitrogen and phosphorus efficiency?balance method?by 41.3%and 76.4%,respectively.3)Compared with FP1,the N leaching reduced by 31.8%and 19.9%,P leaching 22.2%and 15.4 in treatments of FP1-W and FP1-F,respectively.OPT reduced N leaching by23.4%.NP leaching also reduced in FP2+BC treatment,while OPT+S increased the risk of N leaching in two year experiment under wheat–maize rotation system.In addition,nitrogen leaching was mainly in form of DON,followed by NO₃^--N,and NH₄⁺-N was the lowest.The main phosphorus leaching form was MRP,losses of P forms was in order as MRP>DOP>PP.Overall,less water or fertilizer supply can maintain grain yield,increase the utilization efficiency of nitrogen and phosphorus fertilizer and reduce the leaching loss of nitrogen and phosphorus compared with farmer practice.The application of biochar on the basis of farmer practice tended to increase crop yield,while also can reduces the leaching loss of nitrogen and phosphorus,but does not affect the utilization efficiency of nitrogen and phosphorus fertilizer.The OPT treatment can improve the utilization efficiency of nitrogen and phosphorus fertilizer and reduces the leaching loss of nitrogen and phosphorus,but had risk to lower crop yield.The OPT+S did not affect crop yield,nitrogen and phosphorus utilization efficiency,but increased nitrogen and phosphorus leaching.The application of biochar combined with OPT did not affect the grain yield of wheat/maize,but improved the utilization efficiency of nitrogen and phosphorus fertilizer and reduced the leaching of nitrogen and phosphorus.