通过田间小区试验表明 ,玉米的产量损失与田间杂草密度呈极显著正相关r=0 .9988 。关系式为y =-0 .9752 +0 .0 785x ,(x为每 1m2 杂草数量 )。玉米田杂草的生态经济防除阈值为 80～ 90株 /m2 。玉米田杂草与玉米的竞争临界期为播后 3 2～ 3 5d ,其中以播后 1 5d前除草增产效果最明显 Field plots showed that the yield loss of maize was extremely significantly positively correlated with the weed density in the field (r = 0.9988). The relationship is y = -0.9752 +0 .0 785x, (x is the number of weeds per 1m2). The ecological and economical control weed threshold of corn field is 80-90 plants / m2. The critical period of competition between weeds and corn in corn field was 32 ~ 35 days after sowing, in which the weeding effect was the most obvious 15 days after sowing