通过研究根外追肥对新疆杨株高和保护酶活性的影响规律，用以确定最佳的氮肥喷施浓度，为生产中合理施用氮肥提供理论依据。以1年生扦插新疆杨幼苗为试材，氮肥喷施浓度分别为0%（T1，对照）、0.70%(T2)、1.40%(T3)、2.10%(T4)、2.80%(T5)，小区试验设计，3次重复。试验结果表明，新疆杨株高呈现出随着氮肥喷施浓度增加而增加，T4和T5处理之间无显著差异，显著高于对照；POD活性T4处理在7、8、10月处于最高值，比对照提高162.49%、69.59%、302.24%；SOD活性在8—10月T4处理分别比对照提高21.36%、25.78%、17.29%；PPO酶活性生长期内表现出一直降低的变化趋势，其中T4处理在7、8、10月处于最高值，分别比对照提高87.02%、52.55%、124.54%。综合分析认为，新疆杨育苗中氮肥喷施浓度为2.10%时效果最佳。

By studying the effect of Populus alba var. pyramidalis plant height and protective enzyme activity under foliage spray and determine the optimal spraying concentration of nitrogen fertilizer and provide a theoretical basis for the reasonable application of nitrogen fertilizer production. Test used 1 years old cuttings of Populu alba var. pyramidalis seedlings as materials. Concentrations of nitrogen fertilizer spraying as 0%(T1，CK), 0.70%(T2), 1.40%(T3), 2.10%(T4), 2.80%(T5) plot experiment design and three replications. The results showed that: Populus alba var. pyramidalis plant height showing increased with the increase concentration of nitrogen fertilizer spraying and between T4 and T5 treatment was no significant difference and significantly higher than control. T4 treatment POD activity as the highest value in July, August, October and increased than control 162.49%, 69.59%, 302.24%. T4 treatment SOD activity increased than control 21.36%, 25.78%, 17.29% in august to October; PPO enzyme activity during the growing trend exhibit has been reduced and T4 treatment as the highest value in July, August, October and increased than control 87.02%, 52.55%, 124.54%. Comprehensive analysis that Populus alba var. pyramidalis seedling nitrogen spray concentration of 2.10% best.