不同除草剂对稻田杂草群落演替的影响

为了明确除草剂对稻田杂草群落演替的影响,2001～2004年,连续4年施用7种稻田除草剂控制移栽稻田杂草,每年调查稻田杂草的种类、密度和鲜重,分析稻田杂草种群的变化.结果表明：连续使用同一除草剂对稻田杂草群落演替影响显著,靶标杂草的优势度值与药剂使用年限存在显著的线性或非线性关系：Y=a＋bx或Y=ax^2＋bx＋c;非靶标杂草优势度值与药剂使用年限呈极显著正相关线性关系.不同药剂处理的杂草群落有一定的差异,连续使用二元复配除草剂,杂草群落的均匀度和多样性指数分别为0.40～0.43和1.57～1.84,明显低于单剂处理和对照区,田间主要杂草是陌上菜、水苋、千金子和水莎草,其杂草的鲜重显著低于其它处理.

Effect of different herbicides on shift of weed community in paddy fields

In order to identify the effectiveness of different herbicides on the shift of weed community, herbicides such as the mixture of acetochlor and bensulfuron-methyl, the mixture of propisochlor and bensulfuron-methyl and the mixture of mefenacet and bensulfuron-methyl etc were applied sequently at recommended dosages for four years to control weeds in transplanted rice. The biomass of weeds was investigated in 50 days after transplanted rice once a year and the population of weeds in response to herbicide application was observed. The result showed that there was a close relationship between the structure of weed community and the number of year of herbicide applying. The linear or curse relationship between the abundance of target weed and the years of the herbicide applying, and trend was best fit by the model, Y=a+bx or Y=ax2+bx+c. After four years continuous use of herbicides, the structure of the weed community seemed to difference in different treatments. The marked difference of weed homogeneous degree and index of biological diversity occurred between the combined herbicides and single herbicide. The homogeneous degree and index of biological diversity of weed communities with the combined herbicides were 0.40-0.43 and 1.57-1.84 respectively, and were less than the other treatments in paddy fields. Their weed communities was consist of Lindernia procumbens, Ammannia baccifera, Leptochloa chinensis and Juncellus serotinus and the fresh weight of these weeds were significantly lower than that of other treatments.