As wheat harvest wraps up in the Midwest it’s time to start thinking about cover crops. The window between wheat or corn silage harvest and the end of the growing season can be a favorable time to establish a cover crop, but it is important to plan ahead and
consider your options before moving forward.
Cover crops can help to contribute, retain and efficiently cycle nutrients, suppress weeds, protect the soil from wind and water erosion, and enhance soil quality. However, to maximize the benefits you receive from your cover crop there are two main things to consider: (1) crop selection based on need and (2) seed costs and proper establishment of the crop. Selection depends on what you hope to get from the cover. Are you looking for a crop to add extra nitrogen? Or for a fast growing hay crop for extra forage? Or for a crop to break up soil compaction? Possibly there is a need for some ground to spread excess manure and a cover crop to hold on to that manure.
Many growers will be looking to fill the niche after wheat or corn silage with a cover crop that will winterkill or can be terminated easily in the fall or spring. Therefore an annual crop may provide a good fit. Summer annual legumes such as soybeans, crimson clover, cowpeas or sunn hemp can provide extra nitrogen, and will winterkill. Tillage radish can help to break up compacted layers. Sorghum-sudangrass or millet can be a good choice for producers looking for emergency forage or to simply hold on to the nutrients coming from manure applications. Cool season crops include field peas or red or white clovers. These crops may establish better as we move into cooler fall weather, although N fixation from clovers may be minimal if they are terminated the next spring. Winter rye, oats and triticale are options for fall planting as well. Many cover crop mixtures including small grains and/or legumes along with radishes may have utility; however, remember that timing of establishment is important. Seeding tillage radish after early September may still have benefits, but roots will not develop the girth commonly seen in advertisements.
“Remember the worn-out, but easy-to-forget adage: you get what you pay for.”
When deciding what cover crops to plant, seed cost is a large factor. Seed costs can be high, especially for radish or legumes like crimson clover, and many growers are not interested in investing a lot in cover crop seed. Low cost covers work just fine for some growers depending on expectations. However, if a good, solid stand is desired that is going to produce large amounts of biomass and/or fix significant amounts of nitrogen, then quality seed is important. Remember the worn-out, but easy-to-forget adage: you get what you pay for. That said, return on investment is a very important consideration, which is why crop selection should be done thoughtfully.
Establishment of a cover crop is another area for consideration. Seedbed prep can range from no-till, heavy residue situations to a clean, even surface. Nothing will reduce your return quicker than poor establishment, so the appropriate seeding method to ensure good soil-to-seed contact should be used. For instance, broadcasting into residues, even with subsequent incorporation may
result in poorer soil-to seed contact than drilling. Crop species and seed cost are important drivers when considering planting strategies. Spinning on rye is probably less risky establishment and return-wise as compared to radish or clover.
Seeding rate is another factor that must be managed correctly. Rate recommendations for cover crops vary widely. Make sure to note the germination % on the seed tag and correct for low germination, and use the seed catalog’s recommendation if applicable. Then experiment to see what suits your operation. When working with mixtures using the correct ratio of seed ensures an even stand across species. One last note is that when working with less typical crops, such as radish, be aware of herbicide plant back restrictions that may negatively affect establishment.