Alternative herbicides for pre-harvest desiccation in glufosinate tolerant soybean: effects on defoliation, desiccation, and plant physiology

Glufosinate is often used for pre-harvest desiccation in soybeans, however, its use is not feasible in varieties with tolerance to this herbicide. Thus, the objective of this study was to evaluate the performance of the herbicides amicarbazone, saflufenacil, flumioxazin, diquat, carfentrazone, tiafenacil and florpyrauxifen, applied alone or in combination, for the pre-harvest desiccation of glufosinate tolerant soybean. To this end, a field experiment was conducted in a randomized block design with four replications. Treatments were applied at the R7.3 phenological stage, with evaluations for defoliation, desiccation, grain moisture, membrane damage, fluorescence, and antioxidant enzymes. For defoliation, except for saflufenacil and the untreated control, all the treatments presented values greater than 80% at 10 days after application (DAA). Membrane damage exceeded 60% for protoporphyrinogen oxidase (PROTOX) inhibitors, whereas for florpyrauxifen, it was less than 10%. The application of amicarbazone resulted in an electron transport rate (ETR) of 1.5. In terms of protein expression, the highest levels (22 mg/g FW) were observed for the combination of amicarbazone with florpyrauxifen and diquat. For the antioxidant enzymes peroxidase and superoxide dismutase, the highest expression was observed for florpyrauxifen + saflufenacil, with values of approximately 2.7 × 10-5 mg/g FW, this suggested that products characterized by a delayed expression of phytotoxicity and minimal membrane damage lead to decreased activity of antioxidant enzymes. Thus, in the pre-harvest desiccation of glufosinate-ammonium-tolerant soybean, considering both productive and physiological aspects, diquat, applied alone or in association with other herbicides, stands out as the most promising management alternative