Effects and models of nitrogen, phosphorus and potassium fertilization for Platycodon grandiflorum

The effect functions of nitrogen, phosphorus and potassium application codes on the yield and total platycodin of Platycodon grandiflorum were established by conducting field experiments using three-factor D-saturation optimal design (310). The results show that the effects of nitrogen, phosphorus, and potassium on yield and total platycodin are nitrogen potassium phosphorus and nitrogen phosphorus potassium respectively. The results of the frequency analysis show that for the target yield between 4200 and 4800 kg/ha and confidence interval 95%, the optimal fertilizer application rates of N, P2O5 and K2O, are 83.72119.41, 64.10134.39 and 78.80147.20 kg/ha respectively, and for the total platycodin content over 5.5%, the optimal fertilizer application rates are 113.37140.12, 85.96153.44 and 76.86136.38 kg/ha, respectively. Consequently, the optimal fertilizer application rates for both high yield and high quality of Platycodon grandiflorum are 113.37119.41, 85.96134.39 and 78.80136.38 kg/ha, respectively. The corresponding fertilizer ratio of N:P2O5:K2O is 1:0.721.18:0.661.20.