Objectives The effects of nitrogen, phosphorus and potassium on the growth and bioactive component contents of Codonopsis pilosula were studied, and the optimum rates of N, P and K were proposed using mathematical model, in order to ensure reasonable fertilization for standardized cultivation of Codonopsis pilosula.
Methods Using three−factor D−saturation optimal design, a field experiment was conducted. The effect functions of nitrogen, phosphorus and potassium application codes on the yield, lobetyolin and polysaccharide of Codonopsis pilosula were established, and the optimum rates were calculated by the models.
Results The effect of N, P2O5 and K2O on yield is N > K2O > P2O5, on lobetyolin content is P2O5 > N > K2O, and on polysaccharide is P2O5 > K2O > N. From the results of the frequency analysis, the optimal fertilizer application rates of N, P2O5 and K2O were respectively 128.4−174.1, 49.26−80.41 and 45.31−70.42 kg/hm2 for the target yield between 2100 and 2500 kg/hm2 and confidence interval 95%, and 128.5−196.6, 77.09−118.0 and 41.34−53.72 kg/hm2 for the lobetyolin content over 0.75 mg/g and confidence interval 95%, and 96.04−141.6, 61.53−88.33 and 40.22−75.83 kg/hm2 for the polysaccharide content over 22.50% and confidence interval 95%.
Conclusions The optimal fertilizer application rates for both high yield and high quality of Codonopsis pilosula are N 128.5−141.6, P2O5 77.09−80.41 and K2O 45.31−53.72 kg/hm2, respectively, and the corresponding fertilizer ratio of N:P2O5:K2O is 1:0.54−0.63:0.32−0.42.