Efeito do tempo de dessecação pré-semeadura com 2,4-d na germinação, estande de plântulas e desenvolvimento da soja

Abstract

Due to the presence of weeds in soybean areas, control with herbicide is a common practice. From this perspective, problems such as the unwanted permanence of the active ingredient in the soil causing damage to sensitive crops, such as 2,4-D when sowing does not respect the established grace period, are aggravated. For this reason, the present study aimed to evaluate how the time between pre-sowing desiccation using the herbicide 2,4-D affects soybean development. The experiment was carried out in a field experiment in Laranjeiras do Sul-PR, the soil in the experiment site is a dystrophic red latosol. The experimental design was a randomized block design with 6 treatments corresponding to the time intervals between the desiccation and sowing 0, 1, 4, 7, 14 and 21 days, with 4 replications totaling 24 experimental units. The following variables were evaluated: initial stand, 1000 grain mass, grain yield, plant height at 10 days and spontaneous plant density. Data were subjected to analysis of variance (ANOVA) and subsequent regression analysis, fitting the data to models which best express the relationship between treatments with the respective variables in accordance with the coefficient of determination (R2). It was observed that for the initial stand variable, the treatments where sowing was done after 0 and 1 day after desiccation there was no seedling emergence, being over 90% in the other treatments. For the weight variable of 1000 grains, the treatment with sowing after 21 days of desiccation was highlighted in relation to the other treatments. In the variable height of plants at 10 days after germination, treatments with sowing at 14 and 21 days after desiccation had higher heights. Because of the absence of soybean seedlings emergency, when seeding was performed at 1 day and 0 after desiccation, the incidence of weeds was higher, reaching up to 34 plants per m². For the yield variable, treatment with sowing 21 days after desiccation was the most profitable. The results indicate that when sowing is done 21 days after desiccation the agronomic results are better than the other intervals evaluated, reducing costs and not limiting crop yield.