Effects of straw mulching and nitrogen fertilizer application on nitrogen use in summer maize and soil nitrate content

The current experiment was carried out to study the effects of straw mulching and nitrogen fertilizer application on nitrogen use,grain yield of summer maize and soil nitrate nitrate content.The experiment had 10 treatments: nitrogen rate of N 0,N 90,N 180,N 270,and N 360 kg·hm-2,with and without crop residue incorporation to soil,respectively.The resiults show: compared with the treatments with nitrogen fertilizer only,straw incorporation plus nitrogen fertilizer of N 90,N 180,N 270 and N 360 kg·hm-2 increased nitrogen harvest index by 4.4%,5.6%,3.7%,and 1.9%,respectively,improved crude protein content in grains by 0.6,0.6,0.6,and 0.7 g·kg-1,respectively,increased grain yield by 5.8%,9.5%,10.1%and 9.0% respectively.Meanwhile,nitrate residues in the 0~200 cm soil layer were decreased by 23.8～121.4 kg·hm-2 at the end of summer maize harvest.The results of the preliminary study indicate that straw mulching increased the nitrogen utilization efficiency of summer maize,improved the grain quality,and decreased the nitrate residues in the 0～200 cm soil layer.The optimal amount of nitrogen applied with straw mulching in North Henan is 90～180 kg·hm-2.