氮肥对棉田主要害虫种群密度及棉花产量的影响

通过2年的田间研究，分析了3种不同施氮水平对棉花主要害虫棉玲虫、棉蚜种群动态、棉花蕾铃脱落及棉花产量的影响。结果表明，增施氮肥的棉田棉铃虫和棉蚜数量比对照田要高，但它们之间的差异没有达到显著的水平。不同年份对棉铃虫种群密度有显著影响，但对棉蚜种群没有显著影响。蕾花期施肥可减轻棉铃虫为害造成的花蕾脱落和自然脱落，增加有效铃数和产量，但增加量没有达到显著水平。

Effect of nitrogen fertilizer on pest population and cotton production

Field experiments were conducted from 1999 to 2000 to assess the effect of nitrogen fertilization levels (0.225 and 450 kg.hm-2) on the population dynamics of cotton bollworm (Helicoverpa armigera) and cotton aphid (Aphid gossypii), and on the numbers of cotton buds and bolls in North China. The population densities of cotton bollworm and cotton aphid increased with increasing nitrogen fertilization during 1999 to 2000, but the differences between treatments were not significant (P > 0.05). There were significant differences of cotton bollworm populations and no significant differences of cotton aphid populations between years. Nitrogen fertilization at flower-bud stage decreased the loss of cotton buds and flowers and increased the number of effective bolls and cotton yield, but the decrement and increment did not get to significant level (P < 0.05). No obvious correlations of nitrogen levels with main pest abundance and cotton production were observed.