Abstract: To promote proper fertilization for vegetable farming in open fields, the application rates of NPK fertilizers were studied according to their agronomic benefits on the plants. The 290 field experiments conducted in recent years on leaf mustard (Brassica juncea), Chinese cabbage (Brassica rapa), headed cabbage (Brassica oleracea), lettuce, broccoli, green soy bean, areca taro (Colocasia esculenta), boilen taro (Colocasia esculenta L. Schott.), and carrots allowed a classification on soil fertility using the systematic cluster analysis and significance differentiation test, as well as a proposed recommendation on the fertilization using the ternary non-structural fertilizer efficiency model. The coefficients of variation on vegetable yields were 26.0%-60.2% for the reference and 13.2%-50.3% for a balanced fertilization indicating significant differences on the effect of soil fertility among the various vegetables. For the further experimentation, 4 levels of fertility for the headed cabbages and 3 levels for the remaining 8 vegetables were applied to ensure a significance on the fertilization effect. It was found that all 28 ternary fertilizer efficiency models obtained were typical, and therefore, 9 formulas for the fertilization based on agronomic effect were established. In the following field tests, 14 of them confirmed that the recommended NPK fertilization resulted in an average increase on yield of boilen taros, headed cabbages, green soy beans, and areca taros ranged from 6.8% to 10.6%with a net increasing on revenue of 692 Yuan to 3 834 Yuan per hm² over the conventional fertilization.