CONICET | Buscador de Institutos y Recursos Humanos

Annual wormwood (Artemisia annua L.) interferes with soybean (Glycine max L.) crop growth and yield through competition and allelopathy. Allelochemicals released by the weed may affect the crop directly or indirectly through nitrogen fixing simbionts (Bradyrhizobium japonicum). Crop management imposes stress in the plants that can enhance the amount and the physiological effects of allelochemicals produced by them . The objectives of this work were (i) to study allelopathic and competitive interferences between annual wormwood and soybean crop under field conditions (ii) to describe the crop response to weed interference using non linear models and (iii) to analyze the relative change of competition and allelopathy of plants under sublethal doses of herbicides . Two split plot field experiments with three replications were used. Different weed-crop density levels (competition) were assigned to the main plots while allelopathy (with and reduced) and herbicide (with and without) levels were assigned to the sub-plots. The best descriptions for the soybean biomass/ relative weed biomass and soybean yield/ relative weed biomass relationships at maturity were obtained with the exponential and logistic models respectively. Without herbicide, soybean yield decreased in response to the increase of relative biomass of wormwood when allelopathy was reduced. With allelopathy, soybean yield remained stable as weed relative biomass increased and nodules were larger than without allelopathy. In contrast, with herbicide application a different relationship between soybean yield and relative biomass was observed in plots with allelopathy and reduced allelopathy. The highest allocation to grain yield was attained without herbicide and with allelochemicals.