Persistência e níveis de controle de espécies daninhas com herbicidas em dose recomendada em milho

Abstract

The corn crop is extremely important not only for world food, but also for Brazil's economy. To obtain increasingly more productive rates, the use of chemicals is essential. This work was carried out with the objective of evaluating the control levels and the residual effect on weeds, after the use of the recommended dose of herbicide associations in the corn crop. The experiment was conducted in two stages, in the field and in the greenhouse. In the field stage, conducted in randomized blocks, the following combinations of herbicides were applied after corn seeding: mesotrione+atrazine, atrazine+simazine and tembotrione+atrazine. At intervals of 0, 7, 15, 25, and 35 days after application of the products, soil samples were collected and frozen for use in the second stage, in the greenhouse. All soil samples were thawed on the same day and a bioassay was conducted with the weeds arrowleaf sida, wild poinsettia and black jack. Height measurements were made at 4, 11, 18, 25, and 35 days after sowing (DAS) and green mass at 35 DAS. In the field stage, corn grain yields provided by treatments with the combinations of the herbicides mesotrione+atrazine, atrazine+simazine and tembotrione+atrazine did not differ from each other. The herbicide combinations mesotrione+atrazine and atrazine+simazine exerted weed control at shorter time intervals after application, compared to the tembotrione+atrazine treatment, which provided more efficient control at later intervals after application. Assumptions are made about the different efficiency periods between the treatments with herbicide combinations.