Selection of herbicide for pre-emergence control of volunteer soybean (Glycine max) in maize (Zea mays)

Volunteer soybean is the main weed competing with second-crop maize in Brazil, and options for early control are still limited. Two field trials were carried out in Mandaguaçu (PR) in 2023: one evaluating maize selectivity and another assessing volunteer soybean control. In the selectivity trial, only ametryn and amicarbazone were not selective, reducing maize yield. In the control trial, no treatment achieved 100% control, but amicarbazone (140 and 280 g a.i. ha⁻¹), tembotrione (201.6), terbuthylazine (2800), tembotrione + atrazine (100.8 + 1500) and mesotrione + terbuthylazine (192 + 900) provided efficient control (≥80%) up to 28 DAA. Treatments offering at least 55% early control also resulted in yields similar to the weeded control. Integrating both trials, the best overall results were obtained with atrazine (2500, 5000), mesotrione (192), mesotrione + atrazine (100 + 1000), mesotrione + terbuthylazine (192 + 900), tembotrione, tembotrione + atrazine, terbuthylazine and terbuthylazine + s-metolachlor.