A Study Of Allelopathic Effect Of Water Extracts From Legumes On Three Weeds

Allelopathic suppression to weeds has been focused in recent years as a natural and environment-friendly technique for weed management. Allelopathy researches were begun relatively late in China. The allelopathic suppression effects of rice and wheat on weed had been evaluated, but just little researches had been carried out in forages. Utilization of forages in the weed management is important in agricultural system, because forages, especially legumes have great allelopathic potential.In order to investigate the allelopathic potential of some legume forages, i.e. hairy vetch (Vicia villosa [L.] Roth.) , alfalfa (Medicago sativa L.) , white clover (Trifolium repens L.), red clover (Trifolium pratense L.)and yellow sweetclover (Melilotus officinalis Desr.) on weed germination and seedling growth, laboratory bioassays were conducted with speedwell (Veronica persica Poir.), annual bluegrass (Poa annua L.) and barnyardgrass (Echinochloa crusgalli (L.) Beauv.) as the acceptors. Effects of the water extracts of five legume species at different concentrations(0,0.050, 0.075 and 0.100 g/ml (w/v)) on seed germination and seedling growth of three weed species were investigated. The differences of allelopathic effect among the legume species, growing stage, organs and concentrations were discussted.The results showed that the seed germination and seedling growth of speedwell, annual bluegrass and barnyardgrass were inhibited obviously by applying the water extracts of the legumes, and the inhibition rate increased with the concentration of the water extracts increasing. The allelopathic effects of the legumes on the weeds varied evidently among species. Inhibition rate of five legumes on seed germination and seedling growth of three weed species was hairy vetch and alfalfa > yellow sweetclover > white clover and red clover. The stimulative effect was found by treatment with low concentration extracts of some species. However, inhibitory effect was appeared in high concentration. For example, treatment with the water extracts of white clover promoted the root growth of barnyardgrass less than 0.100g/ml (P>0.05), but it retarded the root growth in 0.100g/ml(P<0.05).The results indicated that the allelopathic effects varied with growing stage. The blooming stage showed significantly stronger allelopathic effects than the branch stage.