Desiccation of Brachiaria ruziziensis with paraquat before soybean sowing

Abstract

Information regarding the desiccation of Brachiaria ruziziensis are scarce in the literature, especially with the use of contact action herbicides. The objective was to evaluate different doses and spray volumes of paraquat in the management of the desiccation of the foraging B. ruziziensis and the effects on soybean crop and weed suppression. The experimental design was completely randomized block with four replications. The treatments were arranged in a factorial scheme 4 x 6 + 1, corresponding to the evaluation of four doses of paraquat (100, 200, 400, and 800 g ha^-1) in six spray volumes (67, 140, 199, 283, 323, and 396 L ha^-1), besides a check without application. To study the population dynamics of the weeds was also used a control in fallow condition and another only with the crop without the presence of straw (weeded). It is concluded that the desiccation of B. ruziziensis with paraquat was effective to 7 days after application, being the highest efficiency obtained from the dose of 200 g ha^-1, regardless of the spray volume used. From this period, the forage plants began a new cycle of growth and interfered negatively on soybean yield. The infestation of weeds was reduced in areas with B. ruziziensis in consortium with soybeans in relation to the fallow area.