Effect of Different Nitrogen Application Rate on Soil Nitrate Nitrogen Distribution,Accumulation and Crop Yields of Northern China Plan

The 8 year-field experiment was carried out to study the effects of nitrogen application rate on soil nitrate nitrogen distribution,accumulation and crop yield.The results showed that the change rule of soil nitrate nitrogen content in 0-200 cm soil layer was N575N400N225N0 after 8 wheat-maize rotation cycle.With the increasing of soil depth,soil nitrate nitrogen content in 0-80 cm soil layer of each treatments decreased,in 60-80 cm reduced to minimum value.With soil depth increasing,the soil nitrate nitrogen in 80-200 cm firstly increased and then decreased,the differences among different treatments increased significantly.The difference reached a significant level for nitrate nitrogen of the same soil layer in 80-200 cm of different treatment.After 8 wheat-maize rotation cycle,the ratio of 100-200 cm soil nitrate nitrogen accumulation of N575 treatment in the total cumulative volume increased 15.18%.By volume of nitrogen and soil nitrate nitrogen accumulation with mathematical model simulation,found two in accordance with the linear relation,nitrogen and soil nitrate nitrogen accumulation amount of regression equation is y = 1.34x+75.58(R2=0.84* *).From the winter wheat and summer maize rotation cycle,the optimum amount of nitrogen is 400 kg/hm2.Considering the effect of nitrogen application rate on soil nitrate nitrogen residue and crop yield,total amount of nitrogen fertilizer application should be about 225-400 kg/hm2 in wheat-maize rotation system at piedmont plain of Huabei.This could basically control soil nitrate nitrogen leaching loss to deep soil and reduce groundwater pollution risk caused by soil nitrate nitrogen leaching.