effects of herbal extracts on red root pigweed (amaranthus retroflexus) and lambsquarters (chenopodium album) weeds in pinto bean (phaseolus vulgaris)

this experiment was set to study the allelopatic effect of aqueous and alcoholic extracts of artemisia, coriander, eucalyptus and cumin on growth of red root pigweed and lambsquarters weeds at laboratory and field in the university of tehran (karaj-iran) in 2008. the herbal plant samples were ground and powdered for extraction preparation, and were mixed with distilled water in a beaker. the extracts were shaked for 72 hours at 25°c, then filtered though paper and centrifuged. laboratory results showed that the extracts of artemisia and cumin prevented the red root pigweed and lambsquarters seed weed germination significantly (p?5%). this effect was greater on red root pigweed germination than that of lambsquarters. for both weeds, the lowest germination was obtained at %100 concentration of alcoholic herbal extract. according to field observation, the alcoholic extracts of cumin and artemisia prevented the red root pigweed and lambsquarters seed germination. so, the highest pinto bean grain and biological yields and pod numbers per unit area acquired. but, the check (no herbal extract) showed the highest weed emergence and together with using trifluralin + one hand weeding gave the lowest pinto bean yields and pod numbers. totally, the alcoholic extracts of cumin and artemisia had the most hindrance effects on red root pigweed and lambsquarters growth, which revealed that in future research allopathic products such as herbal extracts can be used as natural herbicide.