保护性耕作对陇东黄土高原轮作田杂草的影响

以陇东黄土高原旱地连续12年保护性耕作为基础，通过田间取样调查，研究了4种耕作措施下冬小麦-箭筈豌豆-玉米轮作田中杂草的组成和群落特征.结果表明： 不同作物生长期的杂草种类、密度和群落特征各异.免耕使冬小麦生长期杂草密度显著增大，轮作箭筈豌豆后免耕处理的杂草密度变小；秸秆覆盖显著降低了玉米生长期的杂草密度，玉米生长期免耕+秸秆覆盖处理的杂草密度最低.冬小麦和箭筈豌豆轮作前后杂草的群落多样性特征完全相反，从冬小麦生长期到箭筈豌豆生长期，免耕处理杂草群落的多样性指数先高于常规耕作处理，后期低于常规耕作处理；玉米生长期免耕处理的多样性指数均大于其他3种处理.因此，免耕和秸秆覆盖在一些作物生长期能抑制杂草的发生和分布，3种作物轮作对杂草防治具有明显作用.

Effect of conservation tillage on weeds in a rotation system on the Loess Plateau of eastern Gansu,Northwest China.

A field study was conducted to investigate the influences of no-tillage, stubble retention and crop type on weed density, species composition and community feature in a rotation system (winter wheat common vetch maize) established 12 years ago on the Loess Plateau of eastern Gansu. This study showed that the weed species composition, density and community feature varied with the change of crop phases. No tillage practice increased the weed density at maize phase, while rotation with common vetch decreased the density in the no tillage field. Stubble retention reduced the weed density under maize phase and the lowest density was observed in the no tillage plus stubble retention field. No tillage practice significantly increased the weed species diversity under winter wheat phase and decreased the diversity under common vetch phase. At maize phase, a greater species diversity index was observed in the no tillage field. These results suggested that no-tillage practice and stubble retention possibly suppress specific weeds with the presence of some crops and crop rotation is a vital way to controlling weeds in a farming system.