Intervenções na dinâmica populacional de Euphorbia heterophylla L. na cultura da soja

Abstract

Sexual plants of the annual type have a well-defined life cycle, integrating seed formation, seed rain, dispersion, maintenance of seeds in the soil seed bank, germination, growth and development. Several practices favor or reduce the bank, as well as their dispersion and viability, given that seeds are an important component in the dissemination and perpetuation of plants. Knowing this, aimed evaluate the effect of certain management practices as a tool to control and reduce the Euphorbia heterophylla L. seed bank in the soil, using growth regulators and physical methods. To this end, a series of studies were carried out that were framed in four chapters, resulting in 12 experiments, conducted from 2019 to 2022 in the field and in the laboratory, with soybeans as the main crop. The treatments were composed by levels of gibberellic acid, indole butyric acid, hydrogen cyanamide and maleic hydrazide. The latter, under field conditions, was associated with Priori Top® and Fox® fungicides. The first stage focused on reducing the production of dairy seeds (chapter I). Subsequently, avoiding the re-entry or rain of seeds in the soil (Chapter II). Alternatives were sought to make the seeds produced unfeasible (chapter III). And, finally, techniques were used to act on the seed bank, formerly formed and not removed from the area (chapter IV). In order to evaluate the effectiveness of the treatments on the plants, the components of yield, physical and physiological quality of the soybean were evaluated, as well as some variables of growth and development in the dairy plants and the production of seeds, also evaluating their physiological quality. The results obtained allowed us to conclude that the use of maleic hydrazide, associated with the fungicide Priori Top® in the vegetative phase or Fox® in the reproductive phase of dairy plants reduced the number of seeds formed. When using gibberellic acid, the percentage of germination in dairy seeds increased. The opposite was observed for treatments with indole butyric acid and hydrogen cyanamide, which inhibited germination and seedling formation. In turn, the use of maleic hydrazide was effective in reducing the number of seeds and the number of branches in dairy plants, also resulting in a high percentage of unviable seeds.