Subdoses de nicosulfuron em diferentes estádios fenológicos para a supressão de Urochloa brizantha consorciada com milho

Abstract

Intercrop between maize and tropical forages has advantages for the production system, however it is necessary to manage it in order to avoid losses in the yield of the main crop due to competition between species. The objective of the study was to evaluate which nicosulfuron subdose is more efficient to suppress Urochloa brizantha in different phenological stages intercrop with maize grown as a 2nd summer crop. Experiment was carried out at the Universidade Tecnologica Federal do Paraná - UTFPR, Campus Dois Vizinhos, at the 2018/2019 growing season and laid out as a randomized blocks, with subdivided plots, arranged in a 2 x 5 factorial scheme, with 3 replications. Factor A corresponds to the time of application of the herbicide nicosulfuron (between 3-4 leaves and 1 tiller) and factor B to the sub-dose of the herbicide (0, 2, 4, 6 and 8 g ia ha-1, being 0, 50, 100, 150 and 200 ml ha-1of the commercial product Sanson 40 SC). The height, dry matter accumulation per plant (g) and dry mass accumulation (kg ha-1) of U.brizantha were analyzed. Maize morphological characteristic (ear insertion height), yield components (number of grains per row, number of rows and number of grains per ear) and grain yield (kg ha-1) were also evaluated. Application timing and subdoses of nicosulfuron did not affect the height of ear insertion, number of rows and maize grain yield, however it resulted in less height, accumulation of dry mass per plant and accumulation of total dry mass of U.brizantha and greater number of grains per row of maize.