Alelopatia de extratos de plantas de cobertura na germinação e crescimento de plântulas de beterraba e cebola

Abstract

Allelopathy is still a recent subject even though it is documented and studied since many years ago, because the metabolites of secondary route have diverse effects and are produced by plants only under certain circumstances. Therefore, the objective of this research was to verify the potential allelopathic effect of different aqueous extracts of plants used as mulch in no-till vegetable production systems on the germination and growth of beet and onion seedlings. The research was conducted in the laboratory of the Universidade Federal da Fronteira Sul campus Chapecó, with entirely randomized design in a 2x4 factorial scheme (stage of development when the plants were harvested x concentrations of extracts). On onion seeds, extracts of sudão grass, crotalaria and millet plants harvested in vegetative and reproductive stages were evaluated. On beet seeds, extracts from vetch, ryegrass, and rye plants harvested in vegetative and reproductive stages were applied. The extracts were evaluated at concentrations of 0, 25, 50 and 100%. The variables analyzed in both experiments were: germination speed index, first count, germination, aerial part and root length, and aerial part and root dry mass of seedlings. The data were submitted to variance analysis, comparison of means by Tukey's test (p<0.05) for the cover plant stage when harvested and regression analysis for the extract concentration factor. The response of the seeds evaluated with the presence of the extracts was diverse; in general, for Crioula onion seeds, the exposure to crotalaria and millet extracts resulted in negative influence, while the exposure to sudão grass extracts showed varied results, with positive and negative influence. The analyzed variables of the Maravilha beet seeds were benefited with the addition of the extracts of rye grass plants, there was a greater allelopathic potential of the extract of rye grass plants harvested in reproductive stage, however it was possible to observe a beneficial effect with the addition of the extract of rye grass plants harvested in vegetative stage; there was also a beneficial effect with the extract of vetch harvested in vegetative stage and a negative effect only in the maximum concentration of the extract of vetch harvested in reproductive stage.