On June 14, 2023 ICCON kicked off our four-part summer series, Cover Crop Cocktails. The series will feature information on how to design cover crop mixes to address specific goals, including improving pollinator and wildlife habitat, addressing specific field concerns, and taking advantage of the summer window following wheat harvest.
For the first session in the series, ICCON was joined by Morgan Jennings, Field Crops Viability Coordinator with Practical Farmers of Iowa. Morgan shared the what’s, why’s, and how to’s of utilizing cover crop mixes following a small grain harvest – a timely topic given that wheat harvest will soon be here throughout Illinois.
Benefits of utilizing cover crops after a small grain harvest begin even before the cover crop is planted. Simply incorporating a small grain into a typical corn and soybean rotation allows producers to break insect pest and disease cycles that often create problems in corn and soybean rotation systems. The disruption of these cycles, even for just a single year out of three, can bring yield benefits to subsequent cash crops. Taking it a step further – because small grains are harvested in the summer and there is still available growing season to take advantage of, producers are able to include several species of summer annual cover crops that would not be considered for a fall mix. Field work and labor can be spread out a bit more as well which also takes some of the pressure off in the busy fall harvest season.
Summer annual cover crop mixes can provide much needed diversity to the soil biology, improving the diet that soil microbes are typically receiving in a straight corn and soybean rotation. Root exudates from a summer annual cocktail mix can help stimulate segments of the soil microbiome that corn and soybean roots do not typically interact with. This can help prime the soil for the subsequent cash crop the following year. A mix of grasses, brassicas, and legumes can scavenge nutrients, build and protect soil structure, and provide critical nitrogen for a future crop.
For producers who graze livestock, using cover crops after a small grain harvest provides a unique grazing opportunity in addition to the soil benefits. Typically, summer annual mixes can be grazed about a month or so after planting, depending on moisture and other environmental factors. Because of the wide species selections available, producers can mix and match different species based on their goals and management capacities.
Producers are advised, however, to be aware of some additional considerations: when using a common grazing mix of Sorghum, millet, and legumes, farmers should be cautious of prussic acid following a killing frost in the fall and wait about a week after the frost before grazing is resumed. Another consideration, which may be of particular importance for 2023, is nitrate toxicity to livestock. This is most common when drought conditions have occurred, leaving excess nitrate in the soil or in areas where excess nitrogen was applied to the small grain crop but was not utilized by the crop.
Some of the most common species that producers should consider for a summer cover crop mix are:
- Buckwheat – Alleviates compaction; rapid growth; produces viable seed quickly and can become a weed problem
- Sunflowers – Nitrogen scavenger; pollinators
- Sunn hemp – Nitrogen fixation (inoculate seed) does well in heat and would be a good addition to a mix; will kill at first frost
- Sunn hemp + cow peas
- Hairy vetch – Soil builder; weed control; nitrogen fixation
- Radish – Alleviate soil compaction; scavenge nutrients
Each species that is added to a mix brings additional cost and potential management considerations. For a summertime mix, each species should be chosen to include for a specific purpose. Adding a species for the sake of adding a species is likely not going to pay off or provide real advantages if the strengths, weaknesses and compatibilities of that species with other species in the mix are not considered.
For farmers who are new to cover crops, keeping the mix simple is probably best. Start small and figure out what you are comfortable with and be clear about what your goals are. If a small grain is not typically in your rotation, it is worth considering. Find a market for a wheat crop and take the steps to utilize the small grain on a portion of your acres to take advantage of the summer planting window with a cover crop mix that can provide some real agronomic benefits to your production system.
ICCON’s summer series, Cover Crop Cocktails, will continue in July with a presentation on how best to design your cover crop mix rates. 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 email@example.com.