Study on Fertilization Index of Nitrogen,Phosphorus and Potassium for Sweet Potato in Fujian

This paper established a fertilization index of N,P and K for sweet potato production based on 118 field experiments on the fertilizer efficiencies of N,P and K in main production areas of Fujian in recent years.The index included 5 items,such as fertilization effects and soil fertility grading,soil available N,P and K critical indexes,NPK optimum application rate and their proportions in different yield levels,relationship between testing value of soil available NPK and their optimum application rate,and fertilization time and method.Results showed that soil average contribution rate for yield of sweet potato was 62.5%.Applied NPK fertilizers may get significant increasing yield and their average effects ordered as NKP.High yield critical value of soil alkali-hydrolyzable N,Olsen-P and available K were 176 mg kg,17 mg kg and 106 mg kg,respectively.Economic application rates on sweet potato were N 165 kg hm2,P2O5 63 kg hm2 and K2O 204 kg hm2 on average,respectively,and their proportion was 1∶0.38∶1.24.However,the optimum application rates in different soil fertility grades were different.Relationship between soil available NPK testing value and optimum application rate fitted exponential model,and the model realized intention that the fertilization recommendation for plot according to soil testing.The results provided a scientific foundation for highly effective fertilization on sweet potato production in Fujian.