除草剂对棉田杂草群落结构的影响

１９９６－１９９９年连续４年用棉田常用三类除草剂盖草能，乙草胺，草甘膦按常规方法防除棉田杂草，观察一除草剂连续使用后棉田杂种群结构的变化，结果表明，连续使用单一除草剂对棉要草种群结构影响显著，盖草能作用后，禾本科杂草的发生量逐年下降，至第四年已不再发生，而阔叶草的发生量在禾本科杂草被防除的当年即迅速上升，且大大超过对照（不用药）杂草发生总量，乙草胺处理能显著控制杂草的发生量，但残存杂草尤其是阔叶杂草逐年增多，到第三，第四年，田间生物量也接近对照，草甘膦连使用后，虽当年除草效果良好，但次年田间杂草发生基数并未得到控制，禾本科草，阔叶草逐年略有上升，且结构有所变化，阔叶杂草上升量略快于禾本科杂草。

Effects of Herbicides on Weed Community Structures in Cotton Fields

Commonly herbicides for cotton such as haloxyfop,acetochlor andglyphosate were applied directly to the weeds among cotton rows once a year at the dosage of 93.75 g．ai／hm2，562.50 g．ai／hm2 and 750.00 g．ai／hm2 for four successive years（1996～1999).The population of weeds in response to herbicide application was observed．Grassy weeds decreased greatly year by year in haloxyfop treated plots，and almost none of them occurred in the third and the fourth year．With the declining competitiveness of grassy weeds，the broadleaf weeds got more growth advantage，weed density in haloxyfop treated plots was much more than that in the plot without herbicide application （CK） in the first year，and so were both weed density and weed biomass in the following year．Weed density in acetochlor treated plots was much less than that in control plots，but uncontrolled weeds especially broadleaf ones increased yearly，and to the third and the fourth year，weed biomass in the plots was almost the same as that in control plots．In glyphosate treated plots，weeds were suppressed effectively，but both grassy weeds and broadleaf weeds continued to increase yearly，with broadleaf weeds superior to grassy weeds．