The "prevented planting" provisions for crop insurance and planting cover crops on that land is a highly variable subject. Brian Lang, an Iowa State University Extension field agronomist located at Decorah in northeast Iowa, provides the following observations and guidelines. The goal is to help farmers make the best cover crop decisions suited for their situation with prevented planting acres and crop insurance rules.
There are farmer's goals for cheap cover, possible forage use for harvest or grazing in late fall and/or spring. There are also seed availability issues, and crop insurance implications on the choice or choices. The intent of the crop insurance provisions is that farmers don't profit "too much" from another crop. A ton or so of November harvested or grazed forage is okay. Tons of forage per acre may threaten their policy. Farmers need to make certain that the insurance company will permit it. Definitely check with your agent first, as some of these options vary by insurance company. All insurance companies agree that there is no grazing or harvest until November 1, 2013.
1) Spring cereals – oats, spring triticale, barley, spring wheat. If planted in June, they will mature and likely shatter seed by late summer. Shatter seed may produce some volunteer plants in the fall. Mid-season management could be used to mow the small grain before heading and count on regrowth to continue into fall. Or let it produce and shatter grain and disk the mature cereals in late summer to potentially 'plant them' for significant fall growth.
2) Spring cereals – oats, spring triticale, barley, spring wheat. Follow the 'black dirt' option until late summer and then plant these cover crops (i.e. Aug. 1 plus or minus a week). They would provide decent fall growth. They are subject to frost kill, but some forage may still be available to graze November 1.~~~PAGE_BREAK_HERE~~~
3) Winter cereals – rye, winter triticale, winter wheat. Planted in June, they will stay vegetative through the season, offer some grazing in fall, over winter, and grow in spring for harvest or grazing. If the winter cereal is not clipped during the summer (such as around Aug 1 or so) there could be noticeable winterkill. Not a problem if someone is just going to kill it anyway in spring. But if you want forage in spring, a clipping around August 1 or so will setup the forage better for overwintering.
4) Winter cereals – rye, winter triticale, winter wheat. You could just wait (black dirt option) and plant in early August. These crops should overwinter fine, and produce some grazing forage for November 1.
5) Brassicas – tillage radish, turnip, kale, rape and others. If planted in June these crops would likely bolt and produce seed by fall, except for Graza radish (see fourth paragraph from top in this publication.
You could use the 'black dirt' option until mid-July and then plant any of the brassicas. They should provide good grazing in November. They tolerate temperatures into the teens. They are also very good at intercepting and storing nitrogen. And they will winter kill; no need to kill in spring. Any combination of brassica and a small grain like oats is also a good option.
6) Ryegrass. Planted in June, probably OK, should be some forage for grazing in November maybe enough for mechanical harvest if not too many hard frosts. Watch for seed head development in late summer… might want to clip to have a more vegetative growth into the fall.
7) Perennial forage for a future hay field in 2014. Alfalfa or alfalfa-grass mixture. Check with your insurance company as to what they allow.
Brian Lang's thoughts on this option: Planted in June is not recommended. Stay with the 'black dirt' option until early August, then seed. Some insurance companies are saying "Alfalfa is not an approved cover crop, but if it is seeded in the fall (on or after July 1) then it will be a fall seeded crop, and if not hayed or grazed at all in 2013, then it will not be considered a second crop and will not reduce the PP payment." So this would mean no harvest November 1 or later for 2013.~~~PAGE_BREAK_HERE~~~
This may be for the best anyway. If it was harvested that late in fall, you would want to leave 6-inches of stubble. Considering the high cutting height and probability of a lot of frosted off leaves by then, there wouldn't be much of an economic trade-off with harvest costs versus yield potential. Again, check with your insurance company as to what they will allow.
8) Perennial clovers—mammoth, medium red, alsike. Could be included with other forages such as small grains, ryegrass or others to build some nitrogen and organic matter for the 2014 crop. Would overwinter and require tillage or chemical termination in spring.
9) Annual clovers—crimson, berseem. Crimson clover -- a clover used in the southern U.S. for fall-winter-spring cover to build nitrogen and organic matter in the soil. It will winterkill in Iowa. A full stand is 18 to 20 pounds per acre. Use a reduced rate in combination with other forages like oats. It does well on well-drained soils, but does not like wet soil conditions. The seed would need to be inoculated with the correct rhizobia prior to planting, see this link.
Berseem clover is an annual clover sometimes used for emergency plantings in Iowa. As an emergency forage option, it grew well in 1993, but not as well in 1994. It does best under good soil moisture conditions. Establishment is problematic in dry soil conditions. Seed would need to be inoculated with the correct rhizobia prior to planting.
10) Annual warm-season grasses--sudangrass, sorghum-sudangrass, millets, etc.
These grasses require 80 degree F temperatures to grow well. They will not grow much at all in the cooler fall weather and will frost-kill at just 28 degrees F. While they can produce considerable biomass during the summer, depending on killing frosts and cool fall temperatures, it is questionable as to what would be usable forage by November 1.
For additional information on cover crops, read this Iowa NCRS publication "Cover Crops to Improve Soil in Prevented Planting Fields". Be aware that this fact sheet does not directly follow prevent plant rules of RMA crop insurance (i.e. it includes soybeans, and no restrictions on alfalfa), but it may give you some additional ideas on cover crop uses.