Application of ASI systematic approach on balanced fertilization of spinach

In this experiment, the yield and quality of spinach(Spinacia oleracea)were studied by means of ASI system- atic approach. Experiment results indicated that calcium deficit was the most dominant limiting factor, followed by nitro- gen and copper in the laterite derived from granite in Hainan. There was a positive correlation between the rate of N application and accumulated nitrate in spinach (chemical nitrogen fertilizer r=0.9876, organic nitrogen fertilizer r= 0.8175). Yield and accumulated nitrate increased with the augment of nitrogen fertilizer application rate. Accumulated nitrate reached a significant level when the N fertilizer application rate exceeded the recommended rate by ASI. Under optimum fertilizer rate of nitrogen(urea 240 kg/ha), the yield of spinach increased with the increase of Ca application rate. The nitrate content of spinach of calcium treatment recommended by ASI system was the lowest. Under the condition of this experiment, the application of magnesium showed a negative effect. The application of K fertilizer showed a nega- tive effect as well. Accumulated nitrate content of spinach increased with the increasing of magnesium and potassium fer- tilizer. There was a preferable correlation between the yield and quality of vegetable and diagnosis results of ASI systematic approach. Therefore, ASI systematic approach could be applied on spinach balanced fertilization.