| Fertilization plays an important and irreplaceable role in agricultural production. The rotation of winter wheat and summer maize is a main cropping system in the southern region of Shanxi Province.Excessive application of nitrogen fertilizer is quite common in this region, and this may cause a series of problems such as cost increase,waste of fertilizer resources, low nitrogen use efficiency and so on, and will further have a negative impact on the ecological environment. How to develop an integrated management strategy for nitrogen fertilizer application within the rotation of winter wheat and summer maize to achieve the goal of high yield and high efficiency is facing an important problem. Xiangfen farm of stock seed in Xiangfen County of Linfen City was selected as experiment site, and field experiment was conducted to explore the effect of nitrogen distribution (42u kg N/ha) within the rotation of winter wheat and summer maize, At same time, field plot and micro plot experiment was conducted to compare and evaluate the difference of nitrogen use efficiency with difference and trace method. Research results will put forward reasonable ratio of nitrogen fertilizer application to guide local agricultural production. The main results obtained are as follows:1. Under the condition of nitrogen fertilizer application (420kg N/ha) within the rotation of winter wheat and summer maize, yield differences were significant in all N treatment compared with the treatment of without N application. The total yield of wheat and maize were increased by931-1931kg/ha with the ratio of8.4%-17.4%. Yield among the treatments were different, and the yield order from the highest to the lowest were arranged as follows:Treatment5(W55M45)> Treatment3(W45M55)> Treatment4(W50M50)> Treatment2(W40M60)> Treatment6(W60M40)> Treatment1(W0M0). Treatment5(231kg N/ha applied in wheat season with the ratio of55%and189kg N/ha in maize season with the ratio of45%) helped to produce the highest yield (13026kg/ha). As far as winter wheat season was concerned, yield among the treatments of N applied were inceased by277-908kg/ha with the ratio of5.7%-18.7%, comparing to the treatment of without nitrogen application (Treatment1). Treatment3(N application189kg/ha) produced the highest yield by5771kg/ha with the ratio of18.7%, but yield in Treatment6was the lowest with the increase ratio of5.7%. Different treatment in maize season also had different yield performance, which probably were affected by the residual fertility of previous crop. Treatment5helped to produce the highest yield by7590kg/ha with the ratio of21.8%comparing to treatment1,2. As far as nitrogen agronomic efficiency within the rotation of winter wheat and summer maize were concerned, different ratio of nitrogen allocation had different response. Agronomic efficiency of nitrogen in all treatments applied N were obtained by2.2-4.6kg.Treatment5(W55M45) was the highest, and Treatment6(W60M40) was the lowest. The order was: Treatment5(W55M45)>Treatment3(W45M55)> Treatment4(W50M50)> Treatment2(W40M60)> Treatment6(W60M40). Agronomic efficiency of N in winter wheat season had a decreased tendency with the increased rate of N application.3. The response of nitrogen uptake within the rotation of winter wheat and summer maize to different ratio of nitrogen distribution exsited significant differences. Nitrogen uptake of Treatment5(W55M45) was the highest by372.2kg N/ha, but Treatment1(WOMO) was the lowest by only285kg N/ha. When the rate of N application in the rotation was determined, the efficiency of nitrogen use was affected by the amount of nitrogen uptake. Nitrogen use efficiency of Treatment5(W55M45) was the highest by20.8%. It was worth pointing out that the efficiency of nitrogen use in this trial was lower than that in previous years due to the adverse climatic factors such as the continuous low temperature in spring and drought in summer.4. Results showed that net income of the rotation was affected by the ratio of nitrogen application. Treatment5(W55M45) had the highest net income by22146yuan/ha, and Treatment2(W60M40) obtained the lowest by20223yuan/ha. Except for treatment5, net incomes in other treatments were lower than that in Treatment1. The phenomenon which yield increased and net income decreased caused by two aspects, on the one hand, the adverse climatic factors and the price of fertilizer fluctuation5. As a certain rate of nitrogen application, fertilization period also had different response in all treatment applied N. Considered by yield, N uptake, NUE and net income, the effect of twice N application was better than that of at a time,6. Nitrogen use efficiency (NUE) was an important index to evaluate the effect of nitrogen application. The results with two methods of difference and trace indicated that NUE with difference method was higher than that with trace method. NUE with difference and trace method was31.9%and15.4%, respectively. |
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