Study On Nitrogen Utilization And Balance Of Applied Fetrilizer In Vegetable Protected Soils Under Greenhouse In Beijing Suburb

On the basis of applied nitrogen fertilizer, using winter-spring Radish,spring-summer Tomato andcatch Chinese Cabbage as test crops, setting N0(the control, no fertilizer-N),N1(the manure only),N2(the reduced N),N3(the optimized N),N4(the increased N),N5(the customed N) six treatments, thisstudy explored the effect of different nitrogen fertilizer on vegetable yield and economic profit, soilNO-3-N distribution,accumulation and leaching characteristics, crop nitrogen uptake and apparentnitrogen balance of the soil-plant-environment system, in Baimiao vegetable production base,Zhangziying Town, Daxing District, Beijing. The main conclusions are as follows:(1) The reduced N (N2) treatment showed the highest vegetable yield,the best economic profit andfertilizer profit in three cropsforrotations, and there is little significance to continue to increase nitrogenfertilizer, on the contrary, causing the reduction of yield and profit.(2) After three cropsforrotations harvest, accumulation of soil0-400cm NO-3-N of all treatmentstended to increase with the increase of nitrogen application; after Radish harvest, accumulation of soil0-100cm NO-3-N of the accustomed N (N5) treatment (519.42kg/hm2) was significantly higher thanother treatments; after Tomato harvest, accumulation of soil0-100cm NO-3-N of all treatments werehigher than those after Radish season, but there were no significant differences among treatments; afterChinese Cabbage harvest, accumulation of soil0-100cm NO-3-N of the reduced N (N2) treatment wassignificantly lower than N3-N5treatments. Analysis of single season, the quantities of soil NO-3-Nleaching increased with nitrogen fertilizer increased, and the quantities showed lower leaching in theearly and higher in the top dressing and harvest stage in Radish and Tomato season. Analysis of annualseason, the quantities of the optimized N (N3),the increased N (N4) and the customed N (N5)treatments were significantly higher than other treatments, there was a phenomenon that the quantitiesof soil NO3--N leaching was low in winter-spring season, high in catch season and higher inspring-summer season. The N uptake of Radish,Tomato and Chinese Cabbage showed a increasing andthen decreasing trend with the increase of nitrogen fertilizer; while the accumulation of the N uptake inRadish season and Tomato season was slow in the early and high in the late; tthe N uptake of thereduced N (N2) treatment in annual season was the highest (356.70kg/hm2), the N use efficiency wasalso the highest (22.02%).(3) In Radish season and Tomato season, the Nmin before sowing and application of nitrogenfertilizer (except for N0treatment) were the main aspects of apparent input; the Nmin after harvest andthe N uptake of plant were the main aspects of apparent output; the apparent balance increasedsignificantly with the increase of nitrogen fertilizer, the apparent balance of the increased N (N4) andthe customed N (N5) treatments in Radish season were significantly higher than that in Tomato season.In Chinese Cabbage season, the Nmin before sowing was the main aspect of apparent input; the Nminafter harvest and the N uptake of plant were the main aspects of apparent output; the apparent balancedescended and there were no significant differences among treatments. The apparent balance of annualseason (y) and nitrogen fertilizer input (x) showed a significant linear relationship: y=1.0665x-65.042, R²=0.9969.Consequently, the reduced N treatment showed the best yield and economic profit, the quantities ofNO₃^--N leaching was lower, and was helped for reducing nitrogen loss, the N uptake and the N useefficiency were both the highest. The reduced N and the optimized N treatments both showed a lowNmin, which was helped for reducing nitrogen loss and stabilizing soil nutrient. The apparent balanceincreased significantly with the increase of nitrogen fertilizer. In the case of high manure, therecommended applied nitrogen fertilizer in vegetable protected soils in Beijing suburb is still high, andthere is further N reduced space.In view of the need of nitrogen of plants and the supply of soil and fertilizer could not besynchronized,high quantities of NO3--N leaching in spring-summer season caused by the high soilmineralization,high initial nitrogen fertilizer input, the reduced N level should be considered as theoptimum nitrogen fertilizer, at the same time, also suggesting that controlling the irrigation water andthe rainfall in spring-summer season, and then to ensure the higher production, the lower nitrogen loss,ultimately achieving favorable economic profit,nutrient profit and environmental profit.