CARACTERIZAÇÃO AGRONÔMICA E QUALIDADE DE SEMENTES DE SOJA SOB A APLICAÇÃO DE HERBICIDAS DESSECANTES EM DOIS ESTÁDIOS REPRODUTIVOS

Abstract

The desiccation of the soybean crop must be carried out in a way that does not impact the productivity of the crop and the quality of the seeds. The prohibition of the herbicide paraquate in the desiccation of soybean points to the need for research with alternative desiccant herbicides, however such products must be used in the phenological stage in which the plant presents physiological maturity. Another problem to be faced by producers in soybean desiccation is the shortage in the market of the main substitute for the herbicide paraquate, diquate, so testing mixtures between herbicides, aiming at dose reduction, is also necessary. Thus, the objective was to evaluate the effects on soybean yield, seed physiological quality, and herbicide performance at different reproductive stages. The experiment was carried out on two soybean cultivars, one with an early cycle (67HO107 IPRO), and the other with a medium cycle (74I77RSF IPRO). A 7 x 2 + 1 factorial scheme was used, represented by 7 desiccant herbicides tested, alone or in combination (factor A) with the time of desiccation (factor B) (phenological stage R7.1 and R7.3), in addition to an additional treatment without application of the desiccant (control). In the cultivar 67HO107 IPRO and 74I77RSF IPRO, the performance of desiccant herbicides and the components of soybean production were evaluated. In the cultivar 67HO107 IPRO, the quality of the seeds was also evaluated. Among the herbicides applied, diquate showed the greatest defoliation and phytotoxicity effect, applied alone or in association with carfentrazone-ethyl. The product [Magnesium Chloride + Phosphoric Acid] and ammonium glufosinate alone or associated with carfentrazone-ethyl are presented as an alternative for desiccation. When the herbicide application occurs at the R7.1 stage, there is a reduction in PMG and seedling dry mass in the cultivar 67HO107 IPRO and productivity in the cultivar 74I77RSF IPRO. Studies still need to be carried out in order to quantify the reductions observed in germination and electrical conductivity for the herbicides [magnesium chloride + phosphoric acid], diquate (200 g/ha) + carfentrazone (24 g/ha) and carfentrazone (40 g/ha) at different phenological stages.