Abstract: In recent years,the effect on potassium fertilizer in paddy field has been obviously going up. It seems to surpass phosphorus fertilizer and even has a tendency to approach the effect of nitrogen fertilizer in Fu-jian. Nitrogen effected well in all sorts of paddy field. If the applying of nitrogen were deficient, the plants showed decreased ear number and effective tillers, increased empty grain, shortten ear, seed weight and yield were also affected.The effect of potassium is very efficient in all sorts of paddy field except salinized soil. If rice were deficient in potassium, the ear would be short, less grain numbers and the thousand-grain weight decreased.In the present, relatively economic and rational quantities for apply ing of nitrogen, potassium and phosphorus, and their proportions are, in early rice, 13.8-15.7kg, the ratio of N:P2O5:K2O equal to 1:0.4-0.5 :0.5-0.75; in late rice, 10.4-15.9kg, N; P2O5:K2O equal to 1:0-0.3: 0.75-1,