Tolerance of cotton to herbicide-coated fertilizers

Abstract Cotton producers need residual herbicides that can safely and practically be applied postemergence. Herbicide-coated fertilizers could allow for simultaneous application of residual herbicides and a bulk fertilizer blend. Therefore, a study was conducted in 2022 and 2023 in Fayetteville, AR, to evaluate cotton tolerance to 12 herbicide treatments coated onto a fertilizer blend and applied over cotton. Herbicides and rates evaluated included diuron at 840 g ai ha −1 , florpyrauxifen-benzyl at 29 g ai ha −1 , flumioxazin at 105 g ai ha −1 , flumioxazin + pyroxasulfone at 70 + 90 g ai ha −1 , fluridone at 168 g ai ha −1 , fluometuron at 840 g ai ha −1 , fomesafen at 280 g ai ha −1 , pyroxasulfone at 128 g ai ha −1 , saflufenacil at 66 g ai ha −1 , saflufenacil + dimethenamid-P at 25 + 219 g ai ha −1 , saflufenacil + pyroxasulfone at 44 + 91 g ai ha −1 , and S -metolachlor at 1,388 g ai ha −1 . In both years, fluridone, fluometuron, diuron, and S -metolachlor caused less than 10% injury at 7 d after treatment (DAT). Higher injury levels were observed in 2022 (19% to 30%) compared with 2023 (4% to 12%) for flumioxazin, fomesafen, saflufenacil, saflufenacil plus dimethenamid-P, and saflufenacil + pyroxasulfone. The elevated injury in one of two years was attributed to the presence of dew when the herbicide-coated fertilizer was applied. The initial injury was transient, as the cotton generally had recovered by 28 DAT for all herbicides. No differences in seed cotton yield or groundcover among the herbicide treatments occurred either year. These results highlight the potential of using several postemergence-applied, residual herbicides coated onto fertilizer that are not currently registered for over-the-top use in cotton.