Effect of Nitrogen Fertilization Distribution on Summer Maize Yield,Net return and Nitrogen Use Efficiency

Nitrogen management remains one of the most challenging tasks forsustainable agriculture.Based on soil analysis and fertilizerrecommendation OPT(N 210,P2O5 90,K2O60 kg/hm2),field experiment was conducted in a randomized design with six treatments and three replicates to study the influence of the distribution of nitrogen application on summer maize yield,net re-turn,and agronomic efficiency of nitrogen application as well as nitrogen use efficiency.The results showed that the distribution of nitrogen application had a significant effect on summermaize yield,net return,the nitrogen content of grain and stalk as well as ni-trogen uptake.The treatment of OPT3(1/2 N applied at V 5-6 stage and 1/2 N as topdressing at jointing stage of maize growth) produced the highest yield and net return by 10 102 kg/hm2 and 15 319 yuan/hm2,respectively.Comparing with the treatment of without nitrogen application(OPT-N),yield and net return increased by 23.4%and 19.3%,respectively.At mean time,agronomic efficiency of nitrogen and nitrogen use efficiency were 9.1 kg and 47.0%,respectively.This indicated that OPT3 was optimum mannerof nitrogen distribution.The treatment of OPT1(N applied at jointing stage of maize growth)helped produce betteryield(9 897 kg/hm2)and net return(14 971yuan/hm2).Compared with OPT-N,yield and net return increased by 20.9%and 16.6%,re-spectively.But nitrogen agronomic efficiency(8.2 kg)and nitrogen use efficiency(38.6%)were lowerthan OPT3.OPT1 also was an option manner.These results will provide theoretic and practice guide forrational fertilization of summer maize in southern region of Shanxi province.