CHEN Erying, QIN Ling, CONG Xinjun, YANG Yanbing, LI Guoyu, KONG Qinghua, GUAN Yan'an
In order to explore the optimum fertilizer application of N, P, K under middle and high soil fertilities, “3414” fertilizer field experiment was conducted to investigate the effect of N, P, K fertilizer application on summer foxtail millet and to optimize fertilizer application rates in Jigu16. The results showed that fertilizer application significantly increased grain yield of foxtail millet by 21.4% and 12.7% in middle and high soil fertilities, respectively. The yield-increasing efficiency of N fertilizer was 20.2% and 7.9%, respectively, the yield-increasing efficiency of P fertilizer was 6.6% and 12.6%, respectively, and the yield-increasing efficiency of K fertilizer was 11.3% and 13.8%, respectively, indicating that yield-increasing efficiency of N fertilizer was the highest at the level of medium fertilities and the yield-increasing efficiency of P and K fertilizer was significantly higher than that of N fertilizer under high fertilities. There were significant interactions among N, P, K fertilizer application in middle and high soil fertilities. At the level of medium fertilities, there was inhibition between N and P, and there was a promoting effect between N, P and K, and there was inhibition between N, P and K at high fertilities. Partial factor productivities of N, P, K were 42.1, 50.4, 200.0 and 56.4, 72.4, 283.8 kg·kg-1 in middle and high soil fertilities, respectively, which showed that partial factor productivities of N, P, K were higher in high fertility than that in middle fertility. Agronomic efficiencies of N, P, K were 7.6, 2.8, 14.6 and 3.5, 7.2, 28.3 kg·kg-1 in middle and high soil fertilities, respectively, which showed that agronomic efficiency of N was higher in middle soil fertility than that in the high soil fertility, while agronomic efficiencies of P, K were higher in high soil fertility than that in middle soil fertility. By establishing ternary quadratic fertilizer application models based on yield in middle and high soil fertilities, the recommended optimum fertilizer amounts of N, P2O5 , K2O were 189.3, 61.1, 45.0 , 141.2, 180.0 and 45.0 kg·hm-2, respectively. It was recommended that amount and rate of N application should be increased in middle soil fertility and P, K application should be increased in high soil fertility. The research supplied a theoretical basis and technical support for fertilizer application under different soil fertilities.