BACKGROUND Field experiments were conducted across three sites in Mississippi in 2018 to evaluate carrier volume and spray quality effects on glyphosate‐resistant soybean response to dicamba. Treatments consisted of dicamba (5.6 g a.e. ha−1) plus glyphosate (8.7 g a.e. ha−1) applied to soybean at R1 using 140, 105, 70, 35, 14, or 7 L ha−1. Each carrier volume was applied with TT11002 and XR110015 nozzles which resulted in Fine and Coarse spray qualities, respectively. A colorimetric dye was included in spray solutions to quantify spray coverage of each treatment. RESULTS Spray coverage decreased with carrier volume and ranged from 21% to 3%. Conversely, soybean injury increased as carrier volume decreased. Soybean height 14 days after treatment (DAT) was reduced 34% to 37% from carrier volumes of 70 to 140 L ha−1; however, carrier volumes of 14 and 7 L ha−1 resulted in 45% height reductions. By 28 DAT soybean height was similar among volumes of 35 to 140 L ha−1 (39% to 42% reduction); however, volumes of 14 and 7 L ha−1 resulted in 46% and 51% reductions, respectively. Grain yield was reduced 14% from treatment at 140 L ha−1 and reductions increased with decreased carrier volume to 41% loss at 7 L ha−1. Averaged across carrier volumes, Fine and Coarse sprays caused 30% and 26% yield loss, respectively. CONCLUSION These data suggest that carrier volume profoundly affects soybean response to dicamba. Therefore, soybean response to sublethal dicamba doses applied at a constant carrier volume may not reflect physical drift exposure. © 2021 Society of Chemical Industry

Optimizing overhead irrigation practices will ensure that water loss is minimized, and each unit of water is used most effectively by the crop. In order to optimize overhead irrigation setup, a study was conducted over two years in Mississippi to quantify the optimal overhead irrigation duration and intensity for six soil types commonly found in row-crop production regions in the state. Each soil type was transferred to containers and measured for total water infiltration and water infiltration over time using a two-nozzle rainfall simulator in a track sprayer. The rainfall simulator was calibrated to apply 2.1 mm of water per minute. The rainfall simulator ran on a 2.4 m track for 90 s, with 3.2 mm total water applied during that time. After the 90 s overhead irrigation event, each container was undisturbed for 150 s and assessed for irrigation penetration through the soil profile. Commercially available irrigation nozzles were measured for droplet size spectrum. Results showed that across soil type, organic matter was the primary factor affecting water infiltration through the profile, followed by soil texture. Irrigation nozzle volumetric median droplet sizes ranged from 327 µm to 904 µm. The results will improve overhead irrigation setup in Mississippi, improving irrigation water use efficiency and reducing losses from soil erosion over the application of water and reduced crop yield.

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Hairy buttercup and cutleaf evening-primrose are winter annual weeds that have become more problematic for winter wheat growers in the Southern Great Plains and the Mid-Southern United States in recent years. Little research exists to base recommendations for controlling hairy buttercup in wheat, and little research has been published on cutleaf evening-primrose control in recent years. With growing concerns of increased herbicide resistance among winter annual weeds, incorporating new herbicide sites of action has become necessary. The objective of this study was to assess halauxifen-methyl as a novel herbicide to control these two problematic winter annual broadleaf weeds in winter wheat in Mississippi and Oklahoma. Studies were conducted across four site-years in Mississippi and one site-year in Oklahoma comparing fifteen herbicide programs with and without halauxifen-methyl. Hairy buttercup and cutleaf evening-primrose control was the greatest when a synthetic auxin was combined with an acetolactate synthase (ALS) inhibiting herbicide. Treatments including halauxifen-methyl resulted in the greatest control of hairy buttercup, whereas a synthetic auxin herbicide plus chlorsulfuron and metsulfuron resulted in the greatest control of cutleaf evening-primrose. Halauxifen-methyl is an effective addition for control of winter annual broadleaf weeds like hairy buttercup and cutleaf evening-primrose in winter wheat.

Residual weed control is influenced by herbicide-soil interactions. This study was conducted to determine whether herbicide sorption to soils and subsequent residual weed control can be manipulated with adjuvants included in tank mixtures. The effects of commercially available adjuvants on S-metolachlor and fluometuron sorption in the laboratory and residual control of barnyardgrass with these herbicides under field conditions were investigated on a Mantachie loam, Catalpa silty clay loam, and Marietta fine sandy loam. The addition of an adjuvant never increased herbicide sorption to soil but, rather, had no effect or decreased the sorption of S-metolachlor and fluometuron. In all tested soil types, sorption of S-metolachlor decreased by up to 17.6-fold. In silty clay loam and loam soil types, the adjuvant did not affect fluometuron sorption. However, in fine sandy loam soils, two of four experimented adjuvants decreased sorption of fluometuron to soil particles up to 1.6-fold. Moreover, no adjuvant influenced the residual control of barnyardgrass exhibited by either chemistry. These data indicate that the addition of an adjuvant to S-metolachlor and fluometuron mixtures will not increase their sorption to loam, silty clay loam, or fine sandy loam soils or alter the efficacy of these herbicides under field conditions.