On August 9, 2023 ICCON was joined by Bethany Bedeker, Cover Crop Education Specialist in the Center for Regenerative Agriculture at the University of Missouri at Columbia. Bethany focused on cover crop species and mix considerations for addressing specific field or resource concerns related to soil compaction and weed control for cash crops.
According to Bethany, addressing resource concerns begins with understanding the importance of biodiversity both above and below ground. Above ground diversity is easy to see in a cover crop mix. While diversity below ground is much more difficult to see, it is no less important. Different species have different root structures and different root exudates that stimulate the diverse microbial communities in the soil.
Soil Compaction
When addressing an issue like soil compaction, it is crucial to recognize that cover crops are not a “quick fix.” Using a deep ripper to break up compaction can create immediate results, but ultimately this strategy pushes the problem deeper into the soil profile. Building good soil aggregation is the best answer to alleviating compacted areas of the field. Cover crop species with deep tap roots like radishes can be helpful to physically break up compaction layers and provide a pathway for other roots to access the areas beneath the compaction zone. The fibrous root systems of grass species can also create channels for water movement and help to increase biological activity to rebuild the soil aggregates that have been destroyed. Annual rye grass is a very good option for addressing compaction, but it does need to be managed properly because the above ground growth is not always reflective of its root mass below ground. This can create some challenges with termination if not addressed properly. Triticale or cereal rye can be used in place of annual rye in many cases to avoid some of the stress or uncertainty around annual rye termination.
Using a mix of cover crops not only allows for root structures to break up compacted soil, they also build soil aggregates. Including a mix of fibrous roots and deep tap roots can support goals to address compaction.
Weed Control
When attempting to improve the weed control benefits a cover crop system, Bedeker says the key is quick stand establishment and lots of biomass. For many farmers, growing cereal rye before soybeans has been a tried and true strategy to both reduce weed pressure early in the season but also later in the season when the soybeans can canopy. The lingering cereal rye biomass will provide a physical barrier to potential weeds and can often inhibit weed seed germination through allelopathy.
Referenced in the Managing Cover Crops Profitably book, this mix of cereal rye, hairy vetch, and crimson clover can be a good mix option for weed suppression.
If farmers are not comfortable with cereal rye before corn, there are other available options that can provide some level of weed suppression. Hairy Vetch does a good job of covering the ground and does well in a mix with other species. It does tend to break down quicker upon termination due to its lower carbon to nitrogen (C:N) ratio, but it has the added benefit of providing additional nitrogen to a corn crop. Corn tends to canopy and provide its own shade for weed suppression sooner than soybeans. Because of this, lingering biomass residue is not quite as critical for suppressing weeds, but it should still be a goal to achieve other soil health benefits.
Bethany’s full presentation can be viewed on ISAP’s Youtube channel. The final session in ICCON’s summer series, Cover Crop Cocktails, will take place on September 13 at 9am CT. ISAP will be joined by Tyson Seirer, from Star Seed Inc, who will speak on cover crop mixes that are beneficial for wildlife and wildlife habitat. If you are interested in joining the Illinois Cover Crop On-Farm Network to learn about new research and hear from cover crop specialists across the Midwest, you can register for our monthly calls or join our google group by sending an email to hvanbeck@farmland.org.
