Interseeding of annual ryegrass has been successful for the past five years in southern Quebec and continues to increase in use there, according to Dan Towery. Interseeding is the practice of planting a cover crop when the corn is about V4-V6 stage (about knee high).  Annual ryegrass has been the go-to cover crop but crimson clover and even daikon radish have also been successful.

By the time the annual ryegrass has reached about 4-6 inches, the corn has grown sufficiently to shade it out.  Without sufficient sunlight, the cover crop’s growth stops and it goes dormant. Once the corn starts drying down and sunlight reaches the annual ryegrass, it will begin growing again. This method of seeding allows additional root and top growth, and a better chance of surviving the winter, especially in Northern Corn Belt.

Towery and a few others have been watching this interseeding experiment carefully.  In the past year, he interseeded annual ryegrass plots in various locations from central Michigan south to central Indiana.

“Corn went in late and the cover crop seed was broadcast a little later than normal by the calendar.  However, the warm, rainy period in mid June provided excellent conditions for germination and very good stands resulted in all plots,” Dan said.

Upon checking plots in September there was a good stand on half of the plots but there was no cover crops on the other half.  It’s possible that the annual ryegrass will return when it gets full sun (maybe).  Residual herbicides need to be selected carefully so as not to affect germination.

Several years of additional plot work will undoubtedly yield further information as to the best management practice with interseeding, and whether it’s a good bet for the Northern Corn Belt.  Towery also cautioned that interseeding is currently in conflict with RMA rules for crop insurance. They don’t want farmers trying to collect crop insurance if, for instance, the interseeded cover crop is blamed for a reduction in corn yield.

In the meantime, he said he’ll collect data on the yields on plots where surviving interseeded cover crops are located. He suggested that, as with any new farm practice, producers should proceed in this endeavor with caution and only on small plots.

Penn State faculty have developed an interseeder which drills the cover crop seed when corn is knee high.  Click here for more on that equipment:  http://extension.psu.edu/plants/crops/soil-management/cover-crops/interseeder-applicator