Correlation Between The Basic Amounts Of Soil Nitrogen Supply Rates On Pakchoi Yield And Nitrogen Use Efficiency

This article, based on objective of the popular green food vegetable among people in Shanghai, known as "pakchoi(Brassica campestris ssp. chinensis L.)", and combined with the technology of formula fertilization by soil testing, aims to figure out the relationship between the soil nitrogen content and the nitrogen fertilizer utilization of "pakchoi", which, in return, contributes to the scientific methodology of the decision of the fertilizer demand of "pakchoi". Under the situation of not affecting the fertility and with the scientific fertilizer usage, the utilization of fertilizers is raised, thus reducing agricultural non-point source pollution and providing some theoretical and practical evidences for improving the quality of the green food vegetables and the hygiene level. The main research results are as follows:The experiment of the soil foundation for nitrogen indicates that, fertilization significantly improves the plant trait and the yield of "pakchoi". The nitrogen content of the "pakchoi" plant rises with the implantation of nitrogen. Soil nutrient contribution rate drops 16.55%, from 77.18% to 60.63%. The fertilizer utilization rate increases 93.2%, from 9.17% to 17.72%. The nitrogen uptake per 100 kg "pakchoi" resides between 4.48 to 4.70 kg, with an average of 4.59 kg, which can objectively reflect the ability of nitrogen supply of the very soil.The experiment of the nitrogen fertilizer planning and management shows that,(1)the mathematical formula based on the field experiment is: y=-0.1756x2+58.606x+13959(R2=0.9276).(2)Given nitrogen fertilizer usage amount as 167kg?hm-2, the yield reaches the highest at 188865 kg. When the usage amount is 210kg?hm-2, the nitrate content in the leafs hits 1724.5mg?kg-1, which is more than those without nitrogen process by 96.6%.(3)It is some kind of non-linear relation between the nitrogen fertilizer usage amount and the nitrogen utilization. With the nitrogen fertilizer usage amount being 150kg?hm-2, the utilization reaches 18.03%.(4)The ratio of base and topdressing being 1:2 benefits the yield and significantly improves the yield of "pakchoi".The research on the interaction of nitrogen fertilizer and phosphate fertilizer reveals that nitrogen and phosphate interaction has a positive effect on improving the plant trait of "pakchoi", and extremely influences the yield. Compared with non-phosphate process, the yield of phosphate process increases 5235kg(6.3%) per hectare.In a brief summary, when the soil foundation for nitrogen is nitrogen uptake per 100 kg of "pakchoi" being between 4.48 to 4.7kg, the optimal nitrogen fertilizer usage amount is suggested as 130 kg to 180 kg per hectare of pure nitrogen; and when the ratio of base and topdressing of nitrogen fertilizer is 1:2, some proper usage of the phosphate fertilizer is conducive to the improvement of yield and the utilization of the nitrogen fertilizer.