The effects of combined application of N、P and K on the yield and quality of onion

The effects of nitrogen, phosphorus and potassium on yield and quality parameters of onion (Allium cepa L) were studied with the design of three factors and quadratic saturation D-optimal regression (310). According to the data obtained, a mathematical model was established, in which N, P and K were independent variables and onion yield and quality parameters were dependent variables. The model analysis showed that N, P and K significantly influenced onion yield and quality parameters, with P having the biggest effect followed by N and K. When N, P and K reached 430.7, 449.5 and 1152.7 kg/hm2, the marginal yield was 0. The interactions of N, K and N, P for onion yield were significant, with the biggest interaction area being N at 240.0#8722;720.0 kg/hm2, P2O5 at 250.0#8722;500.0kg/hm2 and K2O at 600.0#8722;1500.0 kg/hm2. In this experiment, when the fertilizer rates were N at 294.0#8722;480.6 kg/hm2, P2O5 at 332.8#8722;388.5 kg/hm2 and K2O at 861.8#8722;1119.8 kg/hm2, yield reached 75t/hm2 and quality grade passed 90. The most suitable ratio of N: P2O5: K2O was 1:0.93:2.56.