Allelopathic Action of the Níger (Guizotia abyssinica Cass.) on Soybean (Glycine max (L.) Merrill)

Soybean (Glycine max (L.) Merrill) is an agricultural crop with a large increase in production in the last three decades and is an essential component in the manufacture of animal and human food. Understanding the interactions between crop and other plant species used as green manure that can improve yield and so reduce environmental damage. Forages can release secondary metabolites in the environment that influence in a beneficial or harmful way to other plants, characterizing the allelopathy process. The Níger (Guizotia abyssinica Cass.) is used in agricultural systems because it releases allelochemicals, especially flavonoids. Therefore, this study is aimed to evaluate the allelopathic effects of the Niger straw on the germination and initial growth of soybean seedlings. The treatments consisted of aqueous extracts of niger stems, leaves and roots in different concentrations (0; 25; 50; 75 and 100%). For each treatment, five replications were performed, each composed by a 25 seeds distributed in gearbox kept in incubator chamber for 7 days at 25ºC and 12 hours photo period. The experimental design was completely randomized and the data were evaluated by analysis of variance and the means of treatments compared by Tukey’s test at 5% significance. The results show a reduction in germination and initial growth of soybean seedlings submitted to aqueous extract of niger stem and roots. In contrast, the aqueous extract of the Niger leaves increased the length of soybean seedlings. The allelopathic effects of the Niger probably occur due to the presence of flavonoids in the tissues of this plant species.