Dairy School: Cover crops add value to corn silage rotation

Do you plant a cover crop before or after you harvest corn silage?

It’s an option dairy farmers should consider, says University of Wisconsin Extension crops and soils agronomist Heidi Johnson, especially when planting corn after corn. Removing corn silage and then leaving the ground bare risks soil erosion, decreases microbial activity, and reduces the field’s ability to retain nutrients, especially those from a post-harvest manure application.

In this edition of RealAgriculture Dairy School, Johnson shares insights from Wisconsin research on growing continuous corn with cover crops. She explains that researchers have had the most success planting small grains, such as spring barley and oats, with rye and triticale showing the most potential for later planting. “In southern Wisconsin I tell farmers, if it’s before September 20th, you can really go with a spring barley… it will winter kill, but you will have the residue there the next year.” After September 20th, Johnson recommends rye. “It’s very hardy and can grow down to 34 degrees (about 1 degree Celsius). That’s probably the best option when you get late.”

Wisconsin researchers have tested a range of seeding dates. Most of the early-seeding success comes from using a modified drill or using coulters when side dressed N to create better seed-to-soil contact. It’s better than broadcasting because it generates immediate growth to help the seed establish before row closure. In this situation, you need a cover crop that can handle the shade, says Johnson. “Red clover is very much the go-to that we’ve had the most luck with. Annual ryegrass shows promise as well.”

Johnson also emphasizes the need to manage manure application. She says low-disturbance injection systems are good options. When broadcasting manure on a cover crop she stresses that the crop needs to be at least six inches tall to escape damage.

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