Manejo químico de plantas daninhas infestantes da cultura do feijoeiro

Abstract

The bean crop is of great importance for human nutrition. However, weed interference is one of the main factors that causes losses in productivity and quality of harvested grains. Thus, the objective of this work was to evaluate the efficacy, selectivity, and effect of herbicides on the physiology and grain yield components of black beans, applied in pre- and post-emergence of the crop. Two experiments were carried out to test the selectivity and efficacy of herbicides in beans, in randomized blocks with four repetitions. The treatments used were: infested control, weeded control, imazethapyr (53, 79.5, 106 and 127.2g ha-1), imazethapyr+sulfentrazone (53+300, 79.5+300, 106+300 and 127.2+300 g ha-1), imazethapyr+clomazone (53+400, 79.5+400, 106+400 and 127.5+400 g ha-1), sulfentrazone (300 g ha-1), and clomazone (400 g ha-1), totaling 16 treatments. Phytotoxicity was evaluated for the BRS Esteio and SCS 204 Predileto bean cultivars, and the control of alexandergrass and turnip at 07, 14, 21, 28, and 35 days after treatment application (DAT). The gas exchange variables were measured at 30 DAT. In the bean pre-harvest (74 DAT), the number of pods per plant, number of grains per pod, number of grains per plant, weight of one thousand grains, and grain yield were evaluated. The application of imazethapyr+clomazone (106+400 g ha-1) presented the best control of alexandergrass, while the association of imazethapyr+sulfentrazone showed control of turnip above 90%, regardless of the dose used. The highest phytotoxicity was observed in the BRS Esteio cultivar, caused by the application of imazethapyr+sulfentrazone. The results show that the sub-stomatal CO2 concentration, transpiration rate, stomatal water vapor conductance, photosynthetic rate, carboxylation efficiency, and water use efficiency present significant differences with the application of the herbicides on the bean cultivars BRS Esteio. The highest yield of bean BRS Esteio was observed when imazethapyr+clomazone (127.2+400 g ha-1) was applied.