Irrigation and herbicide application timings can affect cotton (Gossypium hirsutum L.) tolerance and weed control when applying herbicide-coated fertilizers, especially herbicides not labeled in the crop, such as florpyrauxifen-benzyl. Experiments were conducted to (1) evaluate the influence of irrigation timing on Palmer amaranth (Amaranthus palmeri S. Wats.) and barnyardgrass control [Echinochloa crus-galli (L.) P. Beauv.], and (2) determine the effect of application timing on cotton injury and Palmer amaranth control with florpyrauxifen-benzyl–coated fertilizer. A greenhouse study was conducted assessing irrigation timings of 0, 3, and 10 d after application (DAA) and five herbicides, including florpyrauxifen-benzyl at 29 g ha-1; fluometuron at 840 g ha-1; fluridone at 168 g ha-1; pyroxasulfone at 91 g ha-1; and S-metolachlor at 1,388 g ha-1. In a field trial at Marianna, AR, application timings comprised 1- to 2-leaf, 3- to 4-leaf, 6- to 8-leaf, and 10- to 12-node growth stages. Generally, activating any herbicide 10 DAA resulted in decreased weed control and increased weed density and biomass compared to 0 and 3 DAA. Under controlled conditions, florpyrauxifen-benzyl provided lowest barnyardgrass control compared to other herbicides. Control of Palmer amaranth was comparable among all herbicides in greenhouse conditions. Application at 1- to 2-leaf, 6- to 8-leaf, and 10- to 12-node growth stages resulted in comparable Palmer amaranth control across years, and injury was less than 20% for all timings. This research underscores the importance of soil moisture and application timing in obtaining optimal weed control and minimal cotton injury when coating herbicides on fertilizer.
