Effective weed control is essential for Kansas grain sorghum producers to achieve strong yields. One of the best management practices for effective weed control is planting grain sorghum into clean, weed-free fields. Grain sorghum planted in a weed-free field, coupled with a strong residual program up front, will start strong and out-compete late-emerging weeds. Also, the chances of chemical weed control failures after crop establishment are higher if grain sorghum is established in an already weed-infested field.
In dryland production systems of western Kansas, conservation tillage is a common practice. This practice helps retain more soil water and increases crop residue on the soil surface, which supports crop intensification. Higher residue amounts also benefit soil health by reducing soil erosion from wind and water, improving soil organic carbon accumulation, and enhancing soil structure. Conservation tillage systems rely on herbicides for effective preplant management of existing weeds, making subsequent weed management strategies more effective.
Preplant herbicide options ahead of grain sorghum are limited, and atrazine has been the basis of most chemical weed control programs in Kansas grain sorghum. Some of the options available are:
Atrazine can be applied as early preplant, PPI, PRE, and POST. It has some activity on grasses like foxtails, but is considered a broadleaf herbicide. It will control susceptible populations of kochia, pigweeds, morningglories, mustards, and ragweeds.
2,4-D. For preplant burndown applications, low-volatile esters are more effective in controlling weeds and are preferably used over amine formulations. But, sorghum can be injured by carryover from preplant 2,4-D. Therefore, growers should follow label guidelines.
Dicamba provides control of susceptible emerged broadleaves and has a moderate residual control of germinating weeds (pigweeds, wild buckwheat, and lambsquarters). Mixtures of dicamba (8 to 16 oz/a) and atrazine (1 to 2 pints/a) in early spring are good options for kochia control.
Glyphosate provides a broad-spectrum control of glyphosate-susceptible weeds present in the field. Glyphosate resistance is widespread in the state, and the herbicide is often mixed with 2,4-D or dicamba for a broader spectrum and increased control.
Sharpen provides control of many broadleaf weeds like common lambsquarters, marestail, mustards, nightshade, Palmer amaranth, redroot pigweed, wild sunflower, and velvetleaf.
Gramoxone can only be handled and applied by certified applicators and is a nonselective, nonresidual contact herbicide often used for preplant burndown of weeds.
Reviton is a new group 14 (PPO-inhibiting) contact herbicide developed for nonselective broadleaf and grass weed control or suppression when applied to actively growing weeds.
Group 15 herbicides. Residual control of weeds that have not emerged can be achieved by including a Group 15 herbicide with a burndown application. S-metolachlor (Dual Magnum, others) can be applied up to 45 days before planting seed treated with Concep III safener. Similarly, if safened seed is used, acetochlor (Warrant, others) or dimethenamid-P (Outlook, others) can be applied. Products that contain pyroxasulfone (Zidua, others) are not labeled for use in grain sorghum.
The use of trade names is for clarity to readers and does not imply endorsement of a particular product, nor does exclusion imply non-approval. Always consult the herbicide label for the most current use requirements and follow all label instructions.
For more detailed information, see the “2025 Chemical Weed Control for Field Crops, Pastures, and Noncropland” guide or check with your local K-State Research and Extension office for a paper copy.
Information provided by Jeremie Kouame, Weed Scientist – Agricultural Research Center, Hays.
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.
