Interest in cover crops has dramatically increased due to their many potential benefits. In addition to conservation purposes, cover crops can provide forage for livestock producers. It is important for livestock producers to consider restrictions on labels of herbicides used earlier in the growing season if they intend to use the cover crop as a forage source. Depending on the herbicide you use, it may restrict your cover crop grazing options.
The two primary reasons for label restrictions related to cover crops are: 1) herbicide residues may prevent successful establishment of the cover crop, or 2) residue tolerances have not been established for the presence of the herbicide within the cover crop. Regardless of the reason for the restriction, failing to follow the restrictions is a violation of the label and therefore a punishable offense.
Livestock producers need to consider grazing restrictions
A new publication from Iowa State University Extension describes your herbicide options for grazing cover crops. The authors are ISU Extension weed management specialist Bob Hartzler; Meaghan Anderson, ISU Extension field agronomist; and Rebecca Vittetoe, ISU Extension field agronomist.
The four-page bulletin has two pages of handy tables which list herbicide products that allow the establishment of cover crops for the purpose of grazing or forage harvest during the same cropping season. The bulletin is titled "Herbicide use may restrict grazing options for cover crops" and the publication number is CROP 3082. You can download it from store.extension.iastate.edu/product/crop3082.
The tables list herbicide products that allow the establishment of cover crops for the purpose of grazing or forage harvest during the same cropping season as application. Herbicides are divided into three categories based on the minimum interval between application and planting of cover crops intended for forage purposes.
Interval between herbicide application and planting cover crop
The first group of herbicides allows planting of the indicated cover crops within four months of application; the herbicide label will list the specific time interval. The second group of products requires a minimum of four months between application and planting of cover crops, whereas a 4.5 month interval is required for the third group.
The authors say the intent of this bulletin is to assist livestock producers in identifying herbicides that are compatible in cropping systems that use cover crops for forage. It is not intended to eliminate the need to read the label and determine specific use restrictions.
Due to the large number of generic and private brand products, not all products are included in these tables, says Hartzler. Inclusion of a product in this bulletin does not imply endorsement of that particular brand, nor does exclusion imply non-approval.
For more on cover crops, click on these links to ISU's online information