| The waste of resources and environmental pollution problems caused by excessive use of nitrogen fertilizer is becoming a very important issue.Rational use of nitrogen fertilizer had become the focus of concern increasingly. In order to provide evidence for reasonable use of nitrogen fertilizer, this paper analyzed the effects of nitrogen level on spring maize nitrogen utilization and soil nitrogen residual. With different level of nitrogen rates (0、84、120、156、192Kg/hm2),this experiment was conducted at Hohhot,Inner Mongolia. The effects on spring maize、Dry matter accumulation、yield、 nitrate-nitrogen accumulation、the absorption of nutrient and N utilization efficiency、the amount of C、N and nitrate-nitrogen in soil were discussed in this paper. The results show as following:1. The aboveground and underground dry matter accumulation were increased with the amount of nitrogen fertilizer increased, the Increase was not obvious after the nitrogen fertilizer level of N156:the application of N fertilizer can significantly increase the ratio of root to shoot, but the difference was not significant, the ratio of root to shoot of N156treatment was maximum.2. The application of N fertilizer can increase the yield, the nitrogen use efficiency ranged from19.7%to25.8%under different rates, and the yield in N156and N192level was significantly higher than others、the highest yield in N156level reaching to11.8t/hm2,but the difference was not significant among the treatments of nitrogen use.3. The application of N fertilizer can significantly increase the content of N in Straw and grain,and it also significantly increased content of K in Straw, but from the increasing effect,but the different application of N fertilizer treatments were not significant.the the content of P in Straw and grain all were not significantly difference among the different treatments.4. With the growth of spring maize, the change of nitrogen accumulation showed "slow-fast-slow" feature. Compared with CK treatment, the nitrogen accumulation of N84. N120, N156and N192treatments increased by19.4%,22.2%,24.9%and21.5%at spring maize ripe stage.Nitrogen fertilizer use efficiency decreased with the increasing of nitrogen,and it decreased greatly from N156level to N192level;The spring maize grain yield the need for nitrogen of each treatment were not significantly different.maintained at2.2-2.3Kg/t. 5. The the content of nitrogen increased with the amount of nitrogen fertilizer increased in vegetative period.The nitrate content of N156and N192was significantly higher than the blank treatment at jointing stage.In the maize tassel period, except N84,other treatments of applicant N fertilizer can significantly increase the content of nitrogen. But compared with the jointing stage,the content of nitrate significantly decreased by1.5-7.0times.6. The differences of soil organic carbon content change between each treatments were not significant. Among all the treatments, only the soil organic carbon content of CK, N84and N156treatment increased,and the increased amount were0.3g/Kg,0.6g/Kg and0.3g/Kg respectively.CK, N84and N156treatments increased soil organic carbon content,and the increase amount were0.3g/Kg、0.6g/Kg、0.3g/Kg respectively. Before sowing of maize,the soil C/N were8.8-9.8,and at harvesting the soil C/N were9.3～10.9.Compared with before sowing, the soil C/N of CK, N84, N120, N156and N192increased by12.9%,10.8%,9.3%,8.6%,11.3%respectively.7. At the ripe stage,the accumulation of nitrate in the0～90cm soil layer increased significantly with nitrogen input increased,and the nitrate nitrogen increased with soil layer depth increasing;the difference of nitrate nitrogen between CK, N84, N120, and N156was not significant,and in the N192level (192Kg/hm2),the nitrate content in deep soil layer was significantly higher than that in surface soil layer. |
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