Eficácia, seletividade e tecnologia de aplicação do ácido pelargônico no controle de plantas daninhas em soja, milho e mandioca

Abstract

Pelargonic acid has excellent potential for use in weed management, however, efficacy and selectivity in soybeans, corn and cassava depend on the dose, number of applications and mode of application. The present study was conducted in two stages. In the first stage, the objective was to evaluate the effectiveness and selectivity of strategies with doses and sequential applications in a directed jet of pelargonic acid in the management of weeds in soybean, corn and cassava crops. For each crop, an experiment was conducted under field conditions in a randomized block design, with four replications. The treatments consisted of sequential application strategies of different doses of pelargonic acid in a protected directed jet, being: an application of 6.5 kg ha-1 (1AP6.5); an application of 13 kg ha-1 (1AP13); an application of 19.5 kg ha-1 (1AP19.5); two applications of 6.5 kg ha-1 (2AP6.5); two applications of 13 kg ha-1 (2AP13); three applications of 6.5 kg ha-1 (3AP6.5); three applications of 13 kg ha-1 (3AP13); weeded control (TC) and non-hoeded control (TNC). In the second stage, the objective was to evaluate the effectiveness and selectivity of pelargonic acid in applications with different tips and spray volumes in controlling weeds in soybean and corn crops. To evaluate the effectiveness of pelargonic acid in controlling the species Conyza bonariensis, Commelina benghalensis and Urochloa brizantha under protected cultivation conditions, an experiment was carried out in a completely randomized design in a 2x4+1 factorial scheme, with four replications. The first factor consisted of two tips (simple fan and double fan for the first experiment and triple and full conical fan for the second test) and the second factor consisted of four application volumes (150, 200, 250 and 300 L ha-1) in addition to a witness without application. Under field conditions, an experiment was conducted for soybean crops and another for corn crops, in a randomized block design in a 2x2+2 factorial arrangement, with four replications. The first factor consisted of two tips (simple and empty conical fan) and the second factor consisted of two application volumes (150 and 260 L ha-1), in addition to two additional controls, one TC and the other TNC. In the first stage, the most efficient strategies consisted of three applications of 6.5 kg ha-1 or two applications of 13 kg ha-1 in the soybean crop, one application of 13 kg ha-1 in the corn crop and two applications of 6.5 kg ha-1 in cassava cultivation to ensure effectiveness and selectivity. In the second stage, it was found that, in general, the use of a volume of 150 L ha-1 provided better results in weed control under greenhouse conditions. Under field conditions, in soybean cultivation, pelargonic acid was effective in controlling weeds, regardless of the tip and volume of application, however more applications and/or association with other management strategies are needed. In corn cultivation, pelargonic acid was effective in controlling weeds and selective, regardless of the tip and volume of application. It is concluded that the strategies for applying pelargonic acid in a protected directed jet were effective in controlling weeds and presents selectivity to soybean, corn and cassava crops, however, for soybean and cassava, sequential applications are necessary, and the recommendations management must prioritize the use of 150 L ha-1 of application volume.