Study on the optimization models of nitrogen, phosphorus and potassium application for Astragalus membranaceus production

The effect functions of nitrogen, phosphorus and potassium application code on root yield and polysaccharide content of Astragalus membranaceus were established based on field experiment using three factor D-saturation optimal design. The results showed that the order of the effect of nitrogen, phosphorus and potassium on yield improvement and polysaccharide was nitrogenpotassiumphosphorus and potassiumphosphorusnitrogen, respectively. The effect of potassium on polysaccharide was negative, but the effects of nitrogen and phosphorus were positive. When the target yield was over 6000–7000 kg/ha, and confidence interval was 95%, the optimum fertilizer application rate was 66.85–102.92 kg/ha, 64.64–94.95 kg/ha, and 119.78～166.48 kg/ha for N, P2O5, and K2O, respectively. When the polysaccharide content was over 13%–14%, and confidence interval was 95%, the optimum fertilizer application rate was 66.85–102.92kg/ha, 64.64–94.95 kg/ha, and 119.78–166.48 kg/ha for N, P2O5, and K2O, respectively. The optimum fertilizer application rate for high yield, efficiency and quality in Astragalus membranaceus production was 99.52–102.92 kg/ha, 94.20–94.95 kg/ha, and 119.78–166.48 kg/ha for N, P2O5, and K2O, respectively. The optimum ratio of N:P2O5:K2O was 1:0.92–0.95:1.16–1.62.