Cover crop misconception: You can’t plant corn after rye cover crop

by Sara Berges,
Allamakee SWCD

We have heard producers say that you’ll have a huge yield drag if you plant corn following a rye cover crop.  Five years ago, this was commonly presented as a potential issue with cereal rye.  However, years of research has shown how to minimize this risk. Most producers (and researchers) have found in recent years that there is little to no yield drag with proper management.

Rye allelopathy was thought to be a potential issue.  While rye does produce allelopathic chemicals that can inhibit the growth of other plants, this has been found to affect plants with small seeds (like many weeds) rather than large corn seeds and is thought to pose minimal risk to corn yield.
Nitrogen management is the biggest issue with corn following rye. One of the benefits of rye cover crop is that it scavenges residual nitrogen in the soil and holds it for the next crop. However, the nitrogen release from the rye tends to occur after corn planting. This means the corn is nitrogen deficient when it begins growth, which can impact yield. One way to mitigate this is to apply starter fertilizer with corn planting. The decaying rye will release nitrogen into the soil later in the growing season.

The timing of rye termination can have a big impact on the following crop. The maturity of the rye at the time of termination will affect its C:N ratio. More mature plants will have a higher C:N ratio and take longer to break down, while younger plants have a lower C:N ratio and take less time to break down. The standard recommendation is to terminate the cover crop 7-14 days before corn planting. However, you can also terminate within 5 days of planting according to RMA. Some producers have found it to be easier to plant into the live cover crop to reduce the likelihood of the rye residue wrapping around their planting equipment.

If you are unsure about planting corn after rye, start with a 10 acre piece to experiment. Most local producers who have tried it have not had yield issues as long as they manage nitrogen and the timing of termination. If you have questions, contact the Waukon NRCS/SWCD office at 563-568-2246 ext. 3.

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