Interferência da chuva no efeito residual do herbicida 2,4-D em latossolo vermelho do cerrado

Abstract

The aim of this work was to evaluate the influence of rain in the residual effect of the 2,4-D herbicide in Oxisol of Cerrado. The experiment was conducted in a greenhouse, in a randomized block design, composed by a factorial 5x3, corresponding to five periods of application before sowing (0, 3, 6, 9 and 12 days before sowing - DBS) and three regimes of simulated rain (0mm, 20mm and 30mm) in four replications, with a total of 60 plots. The herbicide dose was constant (1500 g e.a. ha-1). The residual effect of 2,4-D was evaluated by the emergency speed index (ESI), visual phytotoxicity (% of damage), plant height (cm), dry mass of aerial part and root (g) using soybean as a bioindicator and statistical analysis following the polynomial regression model, at 5% probability. The best emergency speed index occurred in the period of 6 days before sowing with rain of 20mm, the highest phytointoxication and interference in the height of the plants corresponded to periods 0 and 3 days before sowing with no simulated rain (0mm) and the maximum amount of dry mass of aerial part and root were found, respectively, in the period of 9 days before sowing with rain of 20mm and 30mm.