Effects of nitrogen, phosphorus and potassium on the growth and secondary metabolites of Platycodon grandiflorum

Based on the Dsaturation optimal design with three factors of nitrogen, phosphorus and potassium, a field experiment was conducted to investigate the effects of fertilization with different nitrogen, phosphorus and potassium ratios on the growth and effective ingredients of Platycodon grandiflorum. This study showed that the fertilization greatly increased the medicinal yield of P.grandiflorum. The contribution of nitrogen, phosphorus and potassium to the medicinal yield was nitrogenpotassiumphosphorus. The effect of nitrogen, phosphorus and potassium application on the content of platycodin was also following the pattern as nitrogenpotassiumphosphorus. The effect of nitrogen, phosphorus and potassium application on the polysaccharide content was phosphorusnitrogenpotassium. Nevertheless, both nitrogen and phosphorus had a negative effect on the accumulation of total flavone in P.grandiflorum. In terms of the medicinal yield and the content of platycodin, the optimal fertilization combination was 150 kghm-2 N, 79.41 kghm-2 P2O5 together with 225 kghm-2 K2O.