NPK Fertilization for Rice on Fields in Fujian after Vegetable Harvest

Sixty-three field experiments to determine the rice′s responses to NPK fertilizations after vegetable harvest were conducted to establish the optimal fertilization indices for the province.The rice yield under the blank and balanced fertilization showed a linear function mathematically.The average contribution rate of soil nutrients to the rice yield was 79.1%,and the average yield increases attributed to the N,P and K applications were 16.5%,6.7% and 9.0%,respectively.The critical indices of alkali-hydrolyzable N,Olsen-P and available K in the soils of "extremely high fertility" were greater than 230 mg·kg-1,54 mg·kg-1 and 140 mg·kg-1,respectively;less than 200 mg·kg-1,19 mg·kg-1 and 74 mg·kg-1,respectively,in the soil of "low-to-medium fertility";and,in between in the soil of "high fertility".In general,the economic application rates for the soils of extremely high fertility were N 150 kg·hm-2,P2O5 45 kg·hm-2,and K2O 92 kg·hm-2;N 62 kg·hm-2,P2O5 20 kg·hm-2 and K2O 57 kg·hm-2 for the soils of high fertility;and N 120 kg·hm-2,P2O5 37 kg·hm-2 and K2O 40 kg·hm-2 for the soils of low-to-middle fertility.The correlation between the soil analytical results and the recommended fertilizations fitted an exponential model,which would provide a guideline for appropriate fertilization.