Continued above average rainfall from April through May has led to flooded fields and conditions that are too wet to plant or do field work in parts of Iowa. Early June planting decisions surrounding your delayed and prevented planting provision should involve a conversation with your crop insurance provider. The Ag Decision Maker File A1-57 talks about the insurance provision implications related to late planting, prevent planting, and replanting decisions in Iowa. Additionally, there are articles addressing Late Corn Planting Options and Late Soybean Planting Options; these articles discuss late planted yield potential. Each choice has practical and economic implications; approach this decision with caution and with good information.
If a prevented planting provision is taken, it is highly recommended to plant a cover crop or an emergency forage crop (See ICM article, Forage Options with Prevented Planting Fields) rather than letting the field be fallow through the summer. Please discuss this with your crop insurance provider.
Before deciding on a cover crop species for prevent plant fields, read the label from herbicides that were used in the past growing season as well as any that may have been used this growing season. Check for grazing restriction (if applicable), in addition to rotation restrictions before planting to understand any possible herbicide interactions of past herbicides and the cover crop.
Cover Crop Options and Considerations
Soybean can be planted as a prevent plant cover crop option. Soybeans cannot be harvested for grain. It is recommended to plant in rows narrower than 15-inches or broadcast seed. Row crop planters can be used by planting at a ½ seeding rate in the normal row direction followed by planting perpendicular, at an angle, or offset from the original row. Use a seeding rate of 60,000 to 80,000 seeds per acre, and maybe slightly higher if broadcast seeding. Narrower rows and lower seeding rates will support branching to achieve canopy closure more quickly for weed competition. For consideration, soybean might be a viable option to use treated seed that has already been purchased. Soybeans winter kill. Be cautious if corn herbicides were applied before planting as soybeans can be sensitive to those herbicides.
Spring Cereals (Oats, Wheat, Barley) can be planted any time before September 15. When planted early they will likely produce a seed head that will shatter, causing some reseeding. Disking after shattering would help reseed the plants, giving a cover through fall until winter kill occurs.
Brassicas (Turnips, Kale, Forage Rape, Radishes) should be planted from late July into August for best biomass. If planted in June, most of these will likely ‘bolt’ and produce seed by fall. They can be planted with a cereal grain such as oats, triticale, or rye. The brassicas will winterkill, but they are highly frost tolerant and will remain a good grazing forage well into November. Some species of brassicas may have a hard seed coat that may delay emergence. Emergence of seed with hard seed coats may emerge in the spring. 
Legumes (Crimson Clover, Berseem Clover, Field Pea, Hairy Vetch, Common Vetch, Sun Hemp) are slower to establish and more expensive than other cover crop options. Seeding should occur in August to ensure adequate growth that would lead to higher overwintering success.
Winter Cereals (Rye, Wheat, Triticale) can be planted as early as August with good success of winter survival and high forage yield potential in the spring. Minimum seeding rates of 45 pounds per acre for cover, but twice that to maximize a forage harvest in the spring. Rainfall after seeding leads to greater success. Drill seeding is more uniform than broadcast or aerial seeding. Winter cereal rye is generally the most economical. If planting cereal rye early, late summer clipped cereal rye overwinters well, and unclipped cereal rye may have some winterkill. If planting winter cereals in late summer, they would overwinter okay. Termination is needed in the spring for winter cereals.
This article has been adapted from previous ICM News articles written by Stephen Barnhart, Prevented Planting and Cover Crop Considerations, June 2013
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on June 7, 2024. The information contained within may not be the most current and accurate depending on when it is accessed.
Mark Licht Associate Professor
Dr. Mark Licht is an associate professor and extension cropping systems specialist with Iowa State University Extension and Outreach. His extension, research and teaching program is focused on how to holistically manage Iowa cropping systems to achieve productivity, profitability and en...
Gentry Sorenson Field Agronomist in NW Iowa
Gentry Sorenson is a field agronomist in Northwest Iowa for Iowa State University Extension and Outreach. He works closely with farmers to offer educational programming in crop management issues. He also works with agribusinesses, pesticide applicators, certified crop advisors, and other in...
