Hormesis na cultura da soja em resposta à aplicação de 2,4-D sal colina

Abstract

The action of herbicides on plants does not always manifest itself in a deleterious way, because depending on the dose, the effect can even be beneficial. This stimulating effect is known as hormesis. The objective of this work was to evaluate the effects of doses of 2,4-D choline salt on the biometric and yield parameters of soybean sensitive to 2,4-D. Two experiments were conducted, one in a greenhouse and the other in the field, in which fractions were applied at 0 (control); 0.0684; 0.684; 6.84; 68.4 and 684.0 g ae ha-1 of the recommended average dose on the leaflet of the herbicide 2,4-D choline salt at different phenological stages of soybean. The applications of the different 2,4-D salt choline doses were carried out when at least 50% of the plants entered the respective studied phenological stages (V2 and V5 in greenhouse and V2, V5, R2 and two sequential times: V2 and R2; V5 and R2 in the field). In both experiments the treatments effect was evaluated by observing the visual symptoms of injury, the biometric variables plant height, stem diameter, number of leaves, number of branches, dry matter of the aerial part and root and productive as productivity, weight of a thousand grains, number of pods per plant and number of grains per pod of soybeans. The results were submitted to analysis of variance and, when significant, the hormesis model was tested. It was found that doses less than 68.4 g ae ha-1 2,4-D choline salt can increase morphological or productive variables of soybean, and the hormesis regression model used was altered due to exposure at different phenological stages.