种植制度对江苏省棉田杂草群落影响的研究

 经连续5年对江苏省主棉区水旱轮作及旱连作两种种植制度下的棉田杂草种群密度及草害优势度级数进行定田调查，通过时间和空间上的比较统计分析，研究了棉田杂草群落演替趋势及草害发生规律。研究结果表明，种植制度与江苏省棉田杂草群落的组成和草害发生程度紧密相关。在水旱轮作棉田中，随着棉花(Gossypium hirsutum)种植年数的增加，喜湿性杂草稗草(Echinochloa crusgalli)等优势度值逐渐减少，喜旱性杂草马唐(Digitaria sanguinalis)等优势度值逐渐提高，它们之间存在显著的线性关系。旱连作棉田以喜旱性杂草为主，发生量较大，草害较重，年际间杂草群落变化较小。另外，水旱轮作和旱连作棉田之间的杂草群落结构和种群数量差异显著。而地理区域差异的影响明显小于轮作制度差异导致的影响。

THE INFLUENCE OF CROPPING SYSTEMS ON WEED COMMUNITIES IN THE COTTON FIELDS OF JIANGSU PROVINCE

The overall weed infestation indexes and density of all weed populations occurr ing in both the rice_cotton crop rotation and continuous dry_cropping sys tems of the main cotton belts in Jiangsu Province were surveyed over five years continuously. The succession patterns of weed communities and weed occurrence we re studied through statistical analysis in space and time. The results showed th at there was a close relationship between the structure of weed community and th e level of weed infestation and cropping systems. Under the rice_cotton crop rot ation system, the density of hydrophilous weeds such as Echinochloa crusgalli, Alternanthera philoxeroides and Malachium aquaticum was the highest, whi le that of xerophilous weeds (e.g., Digitaria sanguinalis) was lowest. Ho wever, there was marked linear relationship between abundance and time, with abu ndance of hydrophilous weeds (e.g., E. crusgalli) decreasing, and that of x erophilous weeds as (e.g., D. sanguinalis) increasing with time, when cott on was gro wn continuously in the fields with the rice_cotton rotation system. After four years continuous cotton growing, the structure of weed community seemed to tend to stable condition. In the cotton fields with cotton cropping system, there wer e dense density of xerophilous weeds as dominants and no marked change of weed c ommunity structure between different years. Moreover, the marked difference of w eed community structure and weed density occurred between two different cropping systems. The influence of cropping systems on weed community was much more sign ificant than that of geographical factors.