2 合理施肥促进了植株对氮磷钾的吸收积累。膜荚黄芪不同生长时期对氮、磷、钾的吸收量不同，幼苗期、旺盛生长期对氮肥需求量较大，根系膨大期对钾肥的需求量较大。氮磷钾在膜荚黄芪不同器官的含量、吸收积累量及分配比率随着生育时期发生着变化。膜荚黄芪对氮磷钾的吸收积累量随着生育期的推进逐渐增加，至8月16日达到最高，随后呈递减趋势。植株氮磷钾浓度随着生育期的推进小幅升高，至6月14日后呈递减趋势。幼苗期、旺盛生长期氮磷钾主要集中在茎叶中，生育后期氮磷钾主要集中在根系中，这种变化主要是因为膜荚黄芪生长中心的转移。本研究表明，膜荚黄芪植株干物质积累量不仅与氮磷钾的吸收积累总量有关，还随氮磷钾的养分平衡指数直线增加。

4建立了氮磷钾的施肥量编码值与膜荚黄芪根产量、多糖含量的效应函数。结果表明：氮、磷、钾肥对膜荚黄芪根产量的增产作用大小依次为：氮肥>钾肥>磷肥；氮、磷、钾肥对黄芪多糖含量的作用大小依次为：钾肥>磷肥>氮肥，其中钾肥为负效应，氮肥、磷肥为正效应。寻优结果表明，膜荚黄芪目标产量在6000～7000 kg/hm²之间，95%置信区间的优化施肥量为：N 66.85～102.92 kg/hm²，P₂O₅ 64.64～94.95 kg/hm²，K₂O 119.78～166.48 kg/hm²；膜荚黄芪多糖含量在13%～14%之间，95%置信区间的优化施肥量为：N 66.85～102.92 kg/hm²，P₂O₅ 64.64～94.95 kg/hm²，K₂O 119.78～166.48 kg/hm²；膜荚黄芪高产优质高效栽培优化施肥量为：N 99.52～102.92 kg/hm²，P₂O₅ 94.20～94.95 kg/hm²，K₂O 119.78～166.48 kg/hm²，N、P₂O₅、K₂O的最佳比例为：1:0.92～0.95:1.16～1.62。

1 With the passing of growth period, The content of polysaccharide increased progressively; The content of total flavonoids and astragaloside increased gradually, until 16th August. It had a accumulation peak, then decreased gradually. Seedling, vigorous period were key periods to accumulation of polysaccharide; Vigorous periodwas key period to accumulation of total flavonoids and astragaloside.The accumulation peak of active ingredient was lagging behind the accumulation of dry matter.

2 Fertilization promoted the absorption and accumulation of nitrogen, phosphorus and potassium. The absorptive capacity of nitrogen, phosphorus and potassium varied among different developing stages. It needed more nitrogen fertilizer at seedling, vigorous period; more potassium fertilizer at root filling period. With the passing of growth period, the content of nitrogen, phosphorus and potassium of different organs, absorption of nitrogen, phosphorus and potassium, distribution ratio of nitrogen, phosphorus and potassium was changing. With the passing of growth period, the absorption of nitrogen, phosphorus and potassium increased gradually, until 16th august it had a highest absorption, then decreased gradually; the content of nitrogen, phosphorus and potassium increased slowly, until 14th June reached the maximum, then decreased gradually. Because of the growth center transporting, most of nitrogen, phosphorus and potassium concentrate on stem-leaf at seedling, vigorous period; most of them concentrate on root at late growth period. The results showed that dry matter accumulation presented a linear increase tendency with the increasing of the total accumulative amount of nitrogen, phosphorus and potassium, and nutrient balance index .

4 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 nitrogen>potassium>phosphorus and potassium>phosphorus>nitrogen, 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.