By Linda Geist
Soybean makes an excellent choice as a cover crop this year, says University of Missouri Extension soybean specialist Bill Wiebold.
Floods and heavy precipitation kept farmers from planting many Missouri acres in corn and soybean in a timely manner this year. In unplanted fields, Wiebold urges using soybean as a cover crop to protect the soil’s surface. Soybean protects from wind and water erosion, heavy weed growth that adds to the weed seed-bank, and detrimental effects on the soil microbiome. “These effects may influence the field well after this season,” says Wiebold.
Cover crop management and crop choice differ between summer and fall planted cover crops. Heat dictates planting of warm season crops. Cool season crops, usually reserved for fall planting, do not fare well in summer. As a warm season crop, soybean grows quickly. Seed and planting equipment are easily available. Farmers know how to manage soybean, while many do not know how to manage cover crops. As a side benefit, the legume fixes nitrogen.
Before planting a cover crop this year, Wiebold urges farmers to read the latest Risk Management Agency (RMA) Fact Sheet on prevented planting insurance provisions. He also suggests that producers contact their insurance provider and understand deadlines.
“It is critical that producers who are contemplating planting any species of cover crop obtain permission from their crop insurance agent and follow RMA guidelines,” says Wiebold. “Do not put prevented planting insurance benefits at risk by performing an unapproved action. In a year like 2019, with highly unusual weather affecting crop management, it is important to check with regulating agencies often because revised provisions are possible.”
Wiebold offers these practices for best results in planting soybean as cover crops:
1. Broadcast seeding, including by airplane, works for cover crops and with summer annuals such as soybean. However, the soil surface must stay wet during the entire germination process. At a minimum, germination needs five days. Soil surface temperatures in July may exceed maximum for successful germination. Increase seeding rates if broadcast planting. Plant with a row unit or drill for better establishment. Broadcast planting is usually faster.
2. Consider costs when choosing varieties. Do not worry about maturity group or biotech trait. Remember that most patented seed agreements prevent use of grain for planting purposes. Check with your seed dealer.
3. For a cover crop to be successful, it must develop full canopy closure quickly. To help this, plant narrow rows. Choose 15-inch rows over 30-inch rows. Use a drill with row spacing less than 10 inches to increase canopy closure by a few days. Use a 30-inch row planter if that is all you have, says Wiebold.
4. Choose a seeding rate between 60,000 and 100,000 seeds per acre to balance seed expense and soil coverage. More seeds may seem needed for canopy closure advantage, but the difference is too small to balance increased cost.
5. You do not need to use pesticides. There is a small risk of seedling diseases with untreated soybean seeds.
6. Plant into a clean field and scout for weeds after emergence. Cover crops suppress weeds on flooded and prevented planting acres. Apply a post emergence herbicide if weed growth becomes excessive.
Finally, check RMA and insurance guidelines before making any decisions.