Herbicide management for the control of sourgrass and mission grass and forCongo grass suppression Manejo de herbicidas para o controle de capim-custódio, capim-amargoso e supressão de capim-ruziziensis

The advance of intercropping has generated the need for studies that evaluate methods of suppression of forage grasses in order to not harm the development of the commercial culture. The aim of this study is to evaluate the sensitivity of forage grasses to post-emergence herbicide application. To this end, an experiment was carried out in a greenhouse using a randomized complete block design in a 4 x 9 factorial scheme with four replicates. The first factor consisted of the forage grasses Urochloa ruziziensis, Panicum maximum cv. BRS Tamani, P. maximum cv. BRS Quênia, and P. maximum cv. BRS Zuri. The second factor consisted of the combination of eight herbicide treatments applied at post-emergence in association with atrazine (1200 g a.i. ha -1 ), besides a control treatment, without application. P. maximum cv. BRS Quênia was the least sensitive to post-emergence herbicide application. Tembotrione (42 and 84 g a.i. ha -1 ) and mesotrione (48 and 96 g a.i. ha -1 ) have potential for suppression of U. ruziziensis. Tembotrione (84 g a.i. ha -1 ), glyphosate (200 g a.i. ha -1 ), and nicosulfuron (7.8 g a.i. ha -1 ) have potential for suppression of the cv. BRS Quênia, and tembotrione (42 g a.i. ha -1 ) and mesotrione (96 g a.i. ha -1 ) have potential for the suppression of BRS Tamani. The P. maximum cv. BRS Zuri presented a higher plant height, shoot dry matter, and root dry matter than the other forages evaluated. For this forage, the use of nicosulfuron herbicides at post-emergence, regardless of the dose, reduced the shoot dry matter by 70%.

The search for cultivation practices that provide increased soybean yield has been recurrent. From this context, the objective of this study was to evaluate the agronomic performance of soybeans with the application of phytosanitary products, as well as the effect of 2,4-D amine subdoses on this crop. Two field experiments were conducted in a randomized block design (RCBD), in a factorial arrangement, with four replications. In the first experiment, one factor corresponded to the soybean post-emergence application of propiconazole, 2,4-D amine, lactofen, imazethapyr and Grainset ® , while the other factor corresponded to the single or sequential application of these products. For the second experiment, one factor corresponded to the application of 2,4-D amine at two phenological stages of soybeans: V4 or V8 (4 and 8 fully expanded trifoliate leaves, respectively), while in the other factor the subdoses of this herbicide were evaluated: 4.03, 8.06, 12.09, 16.12, 20, 15 and 24.18 g a.i. ha -1 . In both experiments, the additional treatment consisted of the control without application. 2,4-D amine applied in subdoses has potential for use in soybeans. The application of 2,4-D amine subdoses promotes changes in morphological parameters of this crop. Increase in the yield of this crop can be obtained with the application of 2,4-D amine in subdoses varying between 16.12 and 20.15 g a.i. ha -1 .