Sorghum production is gaining traction as growers look for alternatives tied to forage needs, wildlife pressure and specialty markets such as bird seed. As acreage expands, weed management and herbicide selection are becoming increasingly important considerations for producers.
Some farmers are planting sorghum as an emergency forage crop after corn failures, while others are turning to the crop in areas with heavy deer populations because it can experience less wildlife damage than corn. Sorghum also is being grown for bird seed and other uses.
Several herbicides are available for sorghum production, including atrazine, s-metolachlor products such as Dual II Magnum and Bicep II Magnum, acetochlor products including Warrant and Degree Xtra, dimethenamid products such as Outlook, and mesotrione products including Callisto and Lexar. Other herbicides commonly used include dicamba products, 2,4-D, Permit, Peak, Huskie, Maestro, Facet L and Yukon.
While these herbicides are labeled for grain sorghum, not all carry labels for forage sorghum, sudangrass or sorghum-sudangrass hybrids. Pre-emergence herbicides such as atrazine, Bicep II Magnum, Dual II Magnum and Warrant are among the products labeled for forage uses.
Producers also are advised to ensure sorghum seed is treated with a seed safener before planting when using Group 15 herbicides. Common seed safeners include Concep and Screen.
Post-emergence herbicide options for broadleaf weed control include dicamba products, Huskie, Maestro, Peak and Starane Ultra. However, those products do not provide in-crop control of grassy weeds. Newer sorghum technologies, including DoubleTeam used with FirstAct herbicide and igrowth used with ImiFlex, are designed to improve post-emergence grass control.
Growers considering sorghum or other emergency forage crops following failed corn stands also must pay close attention to herbicide rotation restrictions. Labels may limit when rotational crops such as sorghum, wheat or oats can be planted because of crop injury risks or pesticide residue concerns.
Restrictions vary widely by product, ranging from no waiting period to more than two years. Atrazine-containing products typically require at least 10 months before small grains can be planted, making forage sorghum or sorghum-sudangrass more viable alternatives in treated fields.
Some corn herbicides, including Acuron, Corvus and TriVolt, allow wheat planting after four months but require at least 10 months before sorghum can be planted. Other products, such as Bicep II Magnum and similar herbicides, permit immediate planting of sorghum after corn crop failure.
Restrictions can differ significantly among acetochlor-containing products, with some allowing immediate planting of all sorghum types and others limiting forage varieties or delaying planting until the following season.
Because requirements vary by product and crop type, growers are encouraged to consult current herbicide labels before replanting fields after a failed corn crop.
Source: Penn State Extension, "Sorghum Herbicide Options and Other Considerations"