Effect of nitrogen application rate on nitrogen absorption,NO_3-N accumulation in soil and grain yield of winter wheat

Nitrogen fertilizer application was very important to wheat production.In order to clarify the effect of nitrogen fertilizer on nitrogen absorption,NO3-N accumulation in soil and grain yield of winter wheat,a field experiment was conducted with a winter wheat cultivar ‘Gao 8901’ in Gaocheng County,Hebei Province,during 2004-2005.The experiment was arranged by randomized block design,including six treatments of N 0,150,180,210,240 and 270 kg/hm2(expressed in N0,N150,N180,N210,N240 and N270 respectively) with three repeats.The results showed that,in high fertility conditions,with the increase of nitrogen application,the grain yield and N uptake of winter wheat were all increased in the beginning,and decreased thereafter.The highest grain yield and the highest nitrogen absorption were all achieved for the treatment N150,while the highest nitrogen productivity was achieved for the treatment N0.At stem elongation stage and maturity stage,the NO3-N content in soil increased with the increase of nitrogen application amount;the reduction of nitrogen fertilizer application could decrease the NO3-N content in soil within 0～100 cm depth.At stem elongation stage and maturity stage,the accumulation amounts of total N in wheat plants and NO3-N in soil profile were all increased with the increase of nitrogen application amount.However,the increase of the two parameters above were not simultaneously,the increment of soil NO3-N accumulation was much higher than that of total N accumulation in wheat plants.In the scope of nitrogen application of N 0～180 kg/hm2,the total N accumulation in wheat plants increased,and the accumulation of soil NO3-N increased moderately.Supplied with more than N 180 kg/hm2,however,the total N accumulation in wheat plants decreased,while soil NO3-N accumulation increased rapidly.According to the results above,the suitable amount of nitrogen fertilizer application of the winter wheat cultivar ‘Gao 8901’ should be about 150 kg/hm2.