Allelopathic effect of rice leaf extracts on different species of weeds/ Efeito alelopatico de extratos de folhas de arroz sobre diferentes especies de invasoras/ Efecto alelopático de extractos de hojas de arroz sobre diferentes especies de malezas

To reduce the use of herbicides in rice crop it is important to adopt new management methods of weed plants. In view of this, the present study aimed to evaluate the allelopathic potential of aqueous extract of leaves of different rice cultivars in germination and seed vigor of a watergrass (Digitaria ciliaris) and a type of jointvetch (Aeschynomene denticulata). To this end, seeds of these species underwent germination tests: first count of germination, germination speed index, shoot length and root length of seedlings, on germitest paper moistened with water (control) or aqueous extract from fresh leaves of rice cultivars Cica 07, Querencia Roxinho and IRGA 424, at concentrations of 25, 75 and 100%. It is concluded that the fresh leaves of the rice extracts reduce germination and vigor of seeds of both species when at the higher concentrations; however, in low concentrations they can stimulate germination and growth of both species.