Cover crop options for prevent plant acres & drowned-out areas

Anna Cates, Soil health specialist,  Liz Stahl, Extension educator and Phyllis Bongard, Content development and communications specialist

Cover crops seeded mid-season on prevent plant
acres can achieve significant growth and cover
by fall. Photo: Liz Stahl, U of MN Extension

Excessive precipitation and persistently wet conditions have prevented the planting of corn and soybean in some fields and led to ponding and drown-out areas in others. On acres where “prevent plant” is claimed for insurance, the USDA-Risk Management Agency (RMA) requires protection from erosion and control of noxious weeds. Planting a cover crop to these areas can help control weeds and prevent erosion, while enhancing soil structure and preventing “fallow syndrome”.

Fallow syndrome can occur when there is not enough living root material for beneficial soil mycorrhizal fungi to survive. These “good fungi”, also known as AM fungi, facilitate the uptake of nutrients that are less mobile in the soil, such as phosphorus (P) and zinc (Zn). Fallow syndrome has the potential to hurt crop yield the following year. See “Reduce risk of fallow syndrome with cover crops” for more details on this issue.

Considerations when planting a cover crop:

• Check which residual herbicides might be in your soil to give cover crops best chance of success. There is typically little or no information on herbicide labels related to establishment of a cover crop after herbicide application. In general, herbicides with longer residual activity have greater potential to hinder cover crop establishment. Another general guideline is that there tends to be more risk to grass cover crops if a residual grass herbicide was applied, and more risk to a broadleaf cover crop if a residual broadleaf herbicide was applied. Cereal rye and oats tend to be among the most tolerant cover crops to previously-applied herbicides, although this will vary depending on the herbicide applied, application rate, soil type, environmental conditions, and time of application. More details on herbicide interactions with cover crops can be found at: Managing risk when using herbicides and cover crops in corn and soybean. 
• Think ahead to spring 2020. Cover crops that winterkill, such as oats, sudangrass, sorghum-sudangrass, radish, turnip, barley, and crimson or berseem clover, eliminate the need to plan a spring termination. Cover crops such as cereal rye and winter wheat will overwinter. If you’re interested in a cover crop which overwinters, make a plan for termination that fits with your rotation and herbicide program. See Spring management of cover crops for termination options.  
• Select a cover crop to provide coverage throughout the rest of the 2019 growing season. Cost, availability of seed, and when you can plant the cover crop are key factors when deciding what cover crops to plant and whether or not to plant a single species or mixture of cover crops. For example, a mix of radish and sudangrass might promote soil structure and produce a lot of biomass during a hot summer. You can explore species attributes on the Midwest Cover Crop Council website: Cover crop decision tool. Also, consult with your local NRCS to determine approved cover crops and practices on prevent plant acres. 
• Seed a cover as early as possible to compete with weeds. Winter cereals (e.g. rye, winter wheat, and winter triticale) and warm season grasses like sorghum, sudangrass, or sorghum-sudangrass hybrids are favored by planting dates in mid-June through July. When seeded during this time frame, spring cereals such as oat, barley and spring wheat will likely develop a seed head, which could shatter and produce volunteer plants. Brassicas (e.g. radish, turnip, rapeseed) can help break up compaction with their taproots, but some species may bolt and produce seed if planted before August.  
• If it gets late, adapt. Control weeds with an herbicide or tillage before planting a cover crop. If you use an herbicide, keep in mind the potential for herbicides to impact cover crop establishment (see above).  
• Use a reliable seed source. Use good quality seed that has been cleaned, tested for germination and weed seed contamination. Utilize local sources of seed as much as possible to help prevent the introduction of invasive noxious weeds such as Palmer amaranth. Note that if you are considering using bin run seed as a cover crop, be aware that most of the seed purchased today is protected by the Plant Variety Protection Act and other seed laws and regulations. This means that at a minimum most bin run seed cannot be sold or given to another person to plant, and depending on the protections of the seed originally purchased, any planting of the bin run seed may be illegal. More details on MN seed laws can be found at: https://www.mda.state.mn.us/plants-insects/can-i-sell-seed.  
• Utilize available resources. Check out U of MN resources at http://z.umn.edu/cover-crops and be sure to consult with your local NRCS to ensure you have an approved cover crop plan. This NRCS spreadsheet gives recommended seeding rates in different regions of MN as well as information on the qualities of different crops. 

Follow insurance dates and restrictions

• You can plant a cover crop after the “final planting date” for your intended crop (e.g. May 31 for corn across southern MN and June 10 for soybean) and receive a full prevented planting payment. See Prevented planting decisions. 
• To be eligible for the full prevented planting payment, you cannot hay or graze the cover crop before September 1, 2019 or harvest the cover crop at any time. 
• If you plant a cover crop AFTER the “late planting period” (25 days after the “final planting date” for the insured crop) and hay or graze it BEFORE September 1, 2019 you will receive 35% of the prevented planting payment for your first crop. 
• If you plant a cover crop DURING the late planting period (e.g. May 31 + 25 days for corn in southern MN) and you hay or graze your cover crop BEFORE September 1, 2019 you will receive no prevented planting payment. 
• Note that grazing a cover crop BEFORE September 1, 2019 will impact your reportable APH for the year – consult with your crop insurance representative for details if you are considering this option. 
• Be sure to consult with your crop insurance representative for further details and to ensure you are meeting their guidelines and specifications. 

Losing a year’s cash crop is devastating, but planting a cover crop will help ensure that you keep your topsoil in place and possibly even see some soil improvements in the coming years.

For more information on cover crop options and resources on prevent plant, go to Current Issues & Highlighted Resources.

This article was first published in June 2019.