Planting cover crops such as brassicas and small grains during late summer or early fall is becoming a more common and accepted practice.  Photo courtesy of Troy Walz.While the use of cover crops is not a novel production practice, beef producers have turned their focus to capitalizing on the additional forage resource to support the cow herd on top of the added value to the soil profile. However, grazing cover crops does require some management considerations to successfully integrate the row crop and cattle enterprises.

Moisture. Cover crop forages are relatively high in moisture compared to even our vegetative pastures, especially very early on in the cover crop growing stage. The moisture content has a big impact on how much an animal can eat and ultimately, the rate of passage and the amount of nutrients absorbed. Consider feeding a dry roughage source or supplementing cattle while grazing cover crops to optimize forage utilization and cattle performance.

Nitrate Toxicity. Fields that have been heavily fertilized by chemical application and/or livestock manure may be at risk for toxic levels of nitrates, especially if the cash crop was hailed out or if seeded into preventative planting acres. While the risk is probably greater with fall grazing, nitrate toxicity could still be a concern in the spring. The only way to be sure that toxic levels are not present is to test the forage. Providing additional feed resources such as hay and slowly adapting cattle to the cover crop (i.e., only allowed to graze during the day for 1 week) are ways to mitigate the risk.

Sulfur Toxicity. Although brassicas (radishes and turnips) typically winter kill, some brassicas have survived the mild winter this year primarily in the southern parts of the state. Brassicas are naturally high in sulfur and low in fiber so should be seeded with a small grain forage. Limit additional sulfur consumption from water sources and supplemental feeds associated with higher sulfur levels such as distillers grains or corn gluten feed.

Termination. Solely grazing cover crops or mechanically harvesting the forage is not an effective method of termination. Likewise, adequate leaf area needs to be available for herbicide absorption to effectively kill the plant. ISU researchers generally recommend terminating a cover crop 10 to 14 days prior to planting corn to protect yield; however, that time frame is less critical for soybeans. Check with your crop insurance agent for their cover crop termination requirements prior to planting corn or soybeans.

Soil Compaction. Unfortunately, the warmer temperatures and wet conditions are less than ideal for grazing crop residue during the spring. Preliminary ISU research suggests that having a vegetative cover crop may actually help mitigate some compaction concerns while grazing during wet conditions. To minimize compaction risk, consider removing cattle during periods of excess moisture and altering the locations of feeding areas and mineral supply to avoid excessive congregation in a given area.

If you have questions about grazing cover crops this spring, contact your local beef field specialist or agronomy field specialist or see Spring Grazing Cover Crops for more information.

Source: Erika Lundy, Iowa State University Extension