利用吉林省梨树县黑土区氮肥长期定位试验田（施氮水平为0、60、120、180、240、300 kg/hm²），2019～2020两年调查玉米田杂草种类、密度和生物量及其与玉米生物量和产量的关系。结果表明，试验条件下玉米田杂草主要是禾本科杂草，尤其是水稗草Echinochloa oryzoides。与不施肥相比，60 kg/hm²施氮量增加杂草密度和生物量；随氮肥施用量的增加，杂草的密度和生物量均显著降低。在180 kg/hm²供氮量时，杂草的密度和生物量达到最低，分别比60 kg/hm²施氮量的最大值下降81%～94%和90%，玉米产量达到最大。与180 kg/hm²施氮量相比，进一步增加施氮量，玉米产量不增加，杂草的密度和生物量也不再减少。因此，从施肥经济效益和杂草防控两个方面结合考虑，该地区最优施肥量为180 kg/hm²。

The species, density and biomass of weeds in maize fields and their relationship with corn biomass and yield were investigated in 2019-2020 in a long-term nitrogen fertilization field in Lishu county, Jilin province, in which the nitrogen application levels were 0, 60, 120, 180, 240 and 300 kg/ha. The results showed that the weed in maize field was dominated by grass weed, especially Echinochloa oryzoides. Compared with zero fertilization, 60 kg/ha nitrogen input increased weed density and biomass. Then, with the increase of nitrogen fertilizer, the density and biomass of weeds decreased significantly. At nitrogen rate of 180 kg/ha, weed density and biomass reached the lowest, decreased by 81%-94% and 90%, respectively, compared with the maximum at 60 kg/ha nitrogen treatment. Meanwhile, maize yield reached the maximum too. Compared with nitrogen fertilizer at 180 kg/ha, further increase in nitrogen input either increase maize yield nor reduced the density and biomass of weeds. Therefore, considering both the economic benefits of fertilization and weed control, the optimal fertilizer rate for this area is 180 kg/ha.

国家重点研发计划“北方玉米化肥农药减施技术集成研究与示范”（2017YFD0201801）