Estratégias no posicionamento de herbicidas na dessecação pré-colheita da cultura soja

Abstract

Pre-harvest soybean desiccation is an important alternative for anticipating the crop cycle. Paraquat was the main herbicide used in soybean desiccation management, however, after its use was banned, few registered herbicide options remained. Given the above, the objective of this study was to evaluate the use of different herbicide treatments, positioned in isolation and/or associated, in pre-harvest desiccation of soybean crops. For this purpose, a field experiment was carried out, with plants in the R 7.2 phenological stage, where the following treatments were applied(T): (T1)saflufenacil (70 g ha-1 ); (T2)flumioxazim (50 mL ha-1 ); (T3)flumioxazim (100 mL ha-1 ); (T4)glufosinato de amônio (200 g ha-1 ); (T5)glufosinato de amônio (300 g ha-1 ); (T6)glufosinato de amônio (400 g ha-1 ); (T7)diquat (200 g ha-1 ); (T8)diquat (300 g ha-1 ); (T9)diquat (400 g ha-1 ); (T10)glufosinato de amônio + flumioxazim (300+100 mL ha-1 ); (T11)glufosinato de amônio + flumioxazim (300+50 mL ha-1 ); (T12)glufosinato de amônio + flumioxazim (200+100 mL ha-1 ); (T13)glufosinato de amônio + flumioxazim (200+50 mL ha-1 ); (T14)diquat + flumioxazim (400+100 mL ha-1 ); (T15)diquat + flumioxazim (400+50 mL ha-1 ); (T16)diquat + flumioxazim (300+100 mL ha-1 ); (T17)diquat + flumioxazim (300+50 mL ha-1 ) and (T18)control. At 3, 5, 8, and 10 days after application of treatments (DAT) evaluations of desiccation, defoliation, and green percentage analysis were carried out by the image processing and analysis software, ImageJ. At 10 DAT, with the end of the evaluation period, the mass of a thousand grains, and moisture were evaluated. It was observed that at 3 DAT the herbicides flumioxazin, glufosinate ammonium alone and glufosinate ammonium + flumioxazin (1.0 L + 100.0 mL) provided a lower percentage of defoliation, however, at the end of 10 DAT saflufenacil, flumioxazin, diquat, and glufosinate ammonium, at different doses and positions, showed similar results for defoliation, desiccation (visual) and desiccation (image). For defoliation of soybean plants, saflufenacil, and flumioxazin, when applied alone, up to 5 DAT showed lower efficiency, however, the associations of flumioxazin with glufosinate ammonium or diquat provided percentages above 85.0%. For desiccation, both visually and by imaging, at 3 DAT, diquat alone and associated with flumioxazin, and glufosinate ammonium + flumioxazin at the highest dose, provided good results for soybean. All herbicides, in the doses and associations studied, can be used to anticipate the soybean harvest. The herbicides saflufenacil, flumioxazin, diquat, and ammonium glufosinate, in different doses and positions, did not interfere with the thousand grain mass and moisture of the soybeans.