| Vegetables are one of liable nitrate accumulation crops. The experiment was to research the effect of three nutrient elements (nitrogen, phosphorus, potassium) on the nitrate and yield of the flowering Chinese cabbage by the optimum compound design (311-A). The optimum compose in three formulations of nitrogen, phosphorus and potassium was put forward by using multivariate regression analysis methods on computer. These modle formulations were proved to be practicable, at the same time, they were analysised the effect on quality and photosynthesis of the flowering Chinese cabbage. The obtained results are summarized as follows:1. Regressive analysis showed that the optimum compose in formulation III of nitrogen, phosphorus and potassium on nitrate and yield of the flowering Chinese cabbage was 165.3mg/L, 329.2mg/L, 73.9mg/L. Having been confirmed, there were no significant differences in yield of the flowering Chinese cabbage among these formulations, but there were significant differences in nitrate content of the flowering Chinese cabbage among these formulations. It showed the formulation III was practicable. Nitrate content of the flowering Chinese cabbage by formulation III was situated in betweenformulation I and formulation II. However, the nitrate reductase activity of the flowering Chinese cabbage by formulation III was the lowest.2. Results also showed that vitamin C, soluble sugar, chlorophyll in the flowering Chinese cabbage by formulation III were better than formulation I . In formulation III, N content in leaves of the flowering Chinese cabbage was lowest, while P content was highest, K content was situated in between formulation I and formulation II.3. After added lxl0-7g/L 6-BA into formulation III for seven days, nitrate content decreased correlating to increase nitrate reductase activity, and photosynthetic rate was enhanced greatly, but there is no significant differences in transpiration rate of the flowering Chinese cabbage between formulations.
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