Composição da comunidade infestante em sistemas de produção de grãos em função das culturas antecessoras

Abstract

The objective of this study was to evaluate the composition of the weed community under different commercial crops of autumn / winter in succession to soybean cultivation, as well as the similarity of weeds in areas involving soybean and corn cultivation in the summer, in order to identify species capable of adapt to the particularities of the management applied to each of the production systems. The experiment was conducted in a long - term experiment at the Fazenda Experimental de Ciências Agrárias da Universidade Federal da Grande Dourados – UFGD, (Experimental Farm of the Faculty of Agrarian Sciences of the Federal University of Grande Dourados – UFGD). The evaluation of the occurrence of weeds in the field in crops implanted in succession to the soybean crop was evaluated, and the following winter treatments were evaluated: Fallow; Second crop corn; Corn+Brachiária; Brachiaria + Vetch; Vetch + Corn; Canola; Wheat; Corn + C. spectabilis; Safflower; Crotalaria ochroleuca; Crambe; Niger; Vetch; Oats + Turnip + Vetch and Crotalaria spectabilis. The phytosociological characterization of weeds in these crops estimated the density, frequency, dominance and importance value of each species in each area. The areas were still analyzed in terms of species diversity, by the Simpson and Shannon-Wiener indices, and inter-characterized by the similarity matrix of Jaccard, being the treatments grouped by the UPGMA method. For the analysis of similarity, in addition to treatments in succession with soybean, were also taken into account, treatments in succession with summer corn: Oats; Brachiaria + Vetch; Vetch + Corn; Canola; Wheat; Corn + C. spectabilis; Safflower; Crotalaria ochroleuca; Crambe; Niger and Fallow, To verify a possible selection of weed species in production systems, taking into account the predecessor crops. The treatments with: brachiaria, vetch, canola, wheat, crambe, niger, turnip and Crotalaria spectabilis showed high suppressive capacity of weeds. For the similarity of weeds, it was possible to identify a tendency of grouping of the areas as a function of the previous summer harvest - soybean or corn. In the present study, it was observed that soybean cultivation in the summer should be followed by species that present a high amount of straw and that distribute evenly in the area, to reduce the problem with weeds in subsequent cultivation, as well as to reduce infestation of the area in the medium and long term.