Fertilizer Response and Optimum Application Rate of NPK on Sweet Potato

The NPK fertilizer response and its optimum application rate on sweet potatoes was studied by field experiments in Fujian.The results showed that on average,the application of N,P,and K on sweet potatoes increased yield by 27.2%,15.8%,and 26.4%,respectively.The rates of the increase were N KP.The weight ratio of big-medium to small sweet potato was 6.7 in a NPK balanced fertilization.It was significantly higher than the N,P or K deficient controls.The output/input ratio of N and K fertilizers was higher in the summer sweet potatoes than in the autumn crop.However,the P fertilizer’s ratio was higher in the autumn.The optimum application rate for N was 168 kg·hm-2,48 kg·hm-2 for P2O5,and 168 kg·hm-2 for K2O,in the ratio of 1:0.3:1.0 on summer sweet potatoes.For the autumn crop,the optimum application rate was 174 kg·hm-2 for N,57 kg·hm-2 for P2O5,and 200 kg·hm-2 for K2O,in the ratio of 1:0.3:1.2.But obviously,the optimum application rate depends largely on the soil type and its fertility.The NPK balanced fertilization increased yield by 14.9% and net income 3600 yuan per hectare over the traditional practice in a higher yield farmland,or increased yield by 12.0% and income by 2200 yuan per hectare in a medium-low yield farmland.