The influences of different weed communities on cotton growth and yield were studied by setting weed free plots, gramineous weeds plots, sedge plots, broadleaf weeds plots and mixed weeds plots in field of Chiping County in the years of 2011 ~2012. The results showed that the gramineous weeds plots were mainly constituted of Eleusine indica at the density of 338. 75~505. 13 stems per square meter, and the cotton yield loss was 69. 7%~69. 8%. The sedge plots were mainly constituted of Cyperus difformis at the density of 260. 75 stems per square meter, and the cotton loss was 57. 7%~59. 4%. Chenopodium album and Eclipta prostrata were the main species in broadleaf weeds plots at the density of 208. 25~316. 0 stems per square meter, and the cotton yield loss was 87. 5%~88. 9%. The mixed weeds plots were mainly constituted of C. Album, E. Prostrata and E. Indica in 2011, but E. Indica and C. Difformis in 2012 at the density of 366. 00~ 410. 00 stems per square meter with the cotton yield loss as 90. 5%~90.1%. The damage rate per stem rncaused by broadleaf weeds was the largest, followed by sedge and gramineous weeds. Weeds Influenced cotton yield mainly in number of cotton bolls. In weed plots, the number of bolls, boll branches and single boll weight decreased by 45. 2% ~ 87. 3% , 21% ~ 64% and 6. 7% ~ 24. 5% , respectively. In addition, weeds also threatened the cotton seedling protection effect.%于2011 ～2012年在山东省茌平县棉田中人为设置无草区和禾本科杂草、莎草科杂草、阔叶类杂草、混合杂草自然发生区,研究了不同杂草群落对棉花生长和产量的影响.结果表明,禾本科杂草区以牛筋草[Eleusine indica(L.)Gaertn.]为主,总密度为338.75 ～505.13茎/m2,棉花产量损失为69.7％ ～69.8％；莎草科杂草区以异型莎草(Cyperus difformis L.)为主,杂草密度为260.75茎/m2,产量损失为57.7％～59.4％；阔叶类杂草区以藜(Chenopodium album L.)、醴肠[Eclipta prostrata(L.)L.]为主,杂草总密度为208.25 ～ 316.0茎/m2,产量损失为87.5％ ～88.9％；混合杂草区杂草群落2011年主要以藜、醴肠、牛筋草等为主,2012年以牛筋草、异型莎草为主,总密度为366.00～410.0茎/m2,产量损失达90.5％ ～ 90.7％.以杂草单茎危害率衡量不同类型杂草对棉花产量损失的影响依次为阔叶类杂革＞莎草科杂草=禾本科杂草.杂草危害直接影响棉花生长,对棉花产量构成因素均有影响,其中对棉花成铃数影响最大,杂草生长区比无草区成铃数减少45.2％～87.3％,果枝数减少21％～64％,单铃重减少6.7％ ～ 24.5％.此外,杂草的生长也直接威胁到棉花植株的保苗效果.
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