中文摘要：

采用311-A最优混合设计，研究了氮、磷、钾不同配比对毛白杨（Populus tomentosa Carr．）杂种无性系S86号苗高和地径的影响，并建立了回归模型。结果表明，施肥对苗木的生长有显著的促进作用。氮对于苗高的影响最大，磷对于地径的影响最大。苗高和地径随着氮、磷、钾施入水平的提高，呈先增大后减小的趋势。氮与磷的交互作用对地径的影响显著。经模型寻优，毛白杨杂种无性系S86号氮、磷、钾的最适施用量分别为326．55～367．24、175．20-201．90和39．24-45．81kg／hm^2。

英文摘要：

A field experiment with optimal regression design （311-A） was conducted to study the effects of nitrogen, phosphoIus and potassium on the height of seedling and ground diameter of Populus tomentosa clone 586 seedlings. A regression model was established. Results showed that fertilizer had a significant role in promoting the growth of seedlings. Nitrogen was the most important factor affecting seedling height of P. tomentosa seedlings, while phosphorus was the most important factor of ground diameter. With the increasing input of the three factors, the seedling height and ground diameter of the seedlings increased. When the input was beyond a certain level, the seedling height and ground diameter began to decrease. There was a significantly positive interactive effect between nitrogen and phosphorus, but a less interactive effect between nitrogen and potassium and between phosphorus and potassium. The optimal application of nitrogen, phosphorus and potassium of P. tomentosa clone S86 was 326.55-367.24 , 175.20-201.90 and 39.24-45.81 kg/hmE,respectively.