| Potential harm of excessive nitrate in vegetables to human bodies has been deeply concerned by the public. However, studies on the measures to regulate nitrate accumulation in vegetables cultivated with nutrition were limited. Specially, reports about the control of nitrate in vegetable with diffetent nutrition formulation are fewer. In order to reduce the nitrate content in vegetable, in the thesis, "311-A" optimal regression design was used to study the effect of phosphorus, potassium, magnesium compound fertilization treatments on the nitrate, Vc contents and yield of water spinach. In the design, the referential nutrition formulation comes from it of HuaNan Agricultrual University, the aim factors are the yield, nitrate, Vc content etc. in Water Spinach, the controlled variances are P2O5, K2O and Mg. With the help of SAS, the equation between the yield, nitrate, Vc content and P2O5, K2O, Mg were founded, at the same time, Using the optimum finding program and mathematical methods to find the optimal formulation of P2O5, K2O and Mg with high yield, high Vc content and low nitrate content in Water Spinach. The results are showed as follows:1 : The optimal formulation of phosphorus, potassium andmaginesium is, Xl= 1 (68 mg-L"1), X2=1.67 (337.23 mg-L"1). X3=-0.67 (19.31 mg-L"1). Accordingly, The yield is 210.96 g-pot"1, NO3" content is 573.40mg-kg"1FW, Vc content is 228.97mg-kg"1FW.2: Increacing properly the use of phosphorus, that is, from -2(20 mg-L"1) to 0 (52 mg-L"1), can make better the growth and quality of Water Spinach.3: Using moderate or large numbers of potassium [from 0 (222 mg-L"1) to 2 (360 mg-L"1) ] and magnesium [from 0 (24 mg-L"1) to 2 (38 mg-L"1) ] is a good way to produce Water Spinach with high production and good quality.4 : The compound treatment of phosphorus, potassium and maginesium can inhance the yield and Vc content, at the same time, reduce the nitrate content of Water Spinach. |
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