Studies On Soil Nitrate-Nitrogen Accumulation And Leaching At Eggplant Fields

In the intensive open field vegetable production, environmental problems caused by excessive application of nitrogen have become increasingly prominent, and it is in urgent need to carry out relevant basic research. This study is carried out at Beijing Shunyi District at open aluvial region, take eggplant for test crops, focusing on different factors:eggplant nitrogen nutrient use, soil inorganic nitrogen accumulation and dynamics, eggplant seasonal crop nitrogen utilization, and soil-eggplant system nitrogen apparent balance, and obtained the following results:In the study, I set four different factors including inorganic fertilizer, organic fertilizer, irrigation and HA-K by orthogonal design, to study the yield effects and0-2m soil layers’ nitrate accumulation. The four levels of inorganic fertilizer rates are262.5kg N/hm2(N1),412.5kg N/hm2(N2),562.5kg N/hm2(N3) and712.5kg N/hm2(N4). The key factor affected0-2m soil layers’ nitrate accumulation is inorganic nitrogen fertilizer. To study the comparison between different treatments based on SNK grouping, the T2, T3and T5get the higher yields, with their inorganic fertilizer application rates of412.5kg/hm2. But the soil layers’ nitrate accumulation of N2treatment is609.6kg/hm2, higher than the soil layers’ nitrate accumulation when its inorganic fertilizer application rates was262.5kg/hm2. For this study, the appropriate amount of organic fertilizer should be OM1(7.5t/hm2)(in this case the nitrogen content of the commercial organic fertilizer is:1.5%), equal to the nitrogen amount of112.5kg N/hm2. Therefore, for this experiment, the appropriate amount of nitrogen fertilizer recommendations was between375and525kg N/hm2.Futher, I set three different levels of nitrogen fertilizer application rates with N1=450kg N/hm2, N2=675kg N/hm2and N3=937.5kg N/hm2. The0-1m soil profile residual nitrate-N after harvest of different nitrogen levels are:N3> N2> N1, and compared to the amount of soil profile residual nitrate-N of N3and N2treatment, the N1treatment decreased by41.7%and51.5%. Of the N0, N1, N2and N3treatment, the apparent nitrogen balance values were115.2,277.8,312.4and516.7kg/hm2, respectively. With the amount of nitrogen application increasing, the corresponding apparent nitrogen balance value will rise correspondently, and the apparent nitrogen loss of the system is more likely to occur. After N1, N2and N3nitrogen fertilizer treatment, the nitrogen efficiency are:22.78%,14.09%and6.11%, respectively. And the NUE will futher to decline with the increase in the amount of nitrogen fertilizer application. In summary, N1=450kg/hm2is the appropriate amount of nitrogen rates for eggplant in Shunyi district.In2010,Iuse lysimeter based on undisturbed soil columns to study the soil nitrate-N leaching regulations in the vegetable field of Beijing alluvial soil region. The main experimental findings are as follows:Under different nitrogen fertilizer treatments, the average nitrate leaching concentrations were significantly different. Nitrogen fertilizer can significantly increase the nitrate concentration in leaching solution, which is the most important factor to cause the vegetable filed nitrate leaching. With the different irrigation management and HA-K treatment, the average concentration of nitrate leaching and total leaching losses were not significantly different. By sampling the leaching solution at different stages in the growing season and analysising its dynamics of nitrate leaching concentration, the T1, T4and T7treatment which get the lowest nitrate-N average concentration and nitrate-N leaching losses are all treated by N1application (450kg/hm2), the sample concentrations of other treatments are higher than the20mg/L national limits for groundwater sources, and more likely to cause groundwater nitrate pollution.The study made the first application of the model-SMCR_N in vegetable crops at China, a certain amount of work of the introduction of the model and a preliminary assessment of the applicability of the model for Beijing aluvial region. The own crop parameters of the model can be directly applied to the long-eggplant simulation. The configurations of round-eggplant (Beijing eggplant No.1) are different from model’s own eggplant parameter, it need to futher to adjust the relevant parameter values. When crop growth parameter K1=1.4, the model simulation achieves the best performance. When complete the adjustment of growth parameters of K1, simulated N uptake of round-eggplant and got the coefficient of determination (R2)=0.85, which means the model’s predictions of crop N uptake are in good performance.