Cover Crop Considerations After Wheat
– Jason Hartschuh, OSU Extension AgNR Educator, Crawford County
Wheat provides many additional opportunities for your operation. These options include drainage improvements, weed-control timing, double-crop soybeans, double-crop forages, compaction mitigation, and soil building through cover crops. From the time wheat is harvested, there is about nine months for weeds to grow and soil to erode. If double-crop soybeans are not planted, the use of cover crops will protect the soil and assist with weed control. High populations of cover crops provide competition and soil cover to control weeds.
While wheat residue does a decent job of controlling erosion, cover crops can provide increased erosion control. The canopy protects soil from the impact of raindrops, and the roots hold it in place, leading to decreased surface erosion and retention of valuable nutrients. The cover crop acts as a trap to hold nutrients from soil and applications of manure or commercial fertilizer. They do an excellent job of absorbing nitrogen and holding it in plant residue.
The type of crop you choose will determine what benefits you receive. If an operation uses tillage, annual cover crops can still have a benefit for the operation. The best time to till is the following spring, just before planting. The cover crop opens soil and allows it to dry out better in the spring for tillage or no-till planting.
One of the greatest economic benefits of cover crops can be found by using them as a forage. Growers receive the soil protection benefits along with a forage to feed cattle. The most common forages planted after wheat include forage sorghum, sorghum-sudan and oats. Forage sorghum and sorghum-sudan are the highest-yielding and should be planted in early July; they require 100 pounds of nitrogen to maximize yield. Oats should not be planted until Aug. 1, along with an application of 50 pounds of nitrogen. Oats is the only one of these crops with the potential to be made as dry hay. Often though, all of them will need to be harvested as silage or baleage.
Another option for harvest is to graze the cover crop, allowing for more species to be planted — including turnips, radish, clover, peas and many more.
When using cover crops for erosion control, weed control and soil building, there are many species — each with their own benefits to consider. One tool to assist with species selection and seeding rate is the cover crop selection tool from the Midwest Cover Crop Council. If new to cover cropping, you may want to select species that will winter-kill to allow for easier management. Selecting a single species, usually a grass species, allows for herbicide control of weeds.
The two most common annual species are oats and radish. Both will winter-kill and are beneficial to help alleviate soil compaction, assist with nutrient retention and capture nitrogen. Oilseed radish should be seeded at 5 to 10 pounds per acre, and oats at 1 to 2 bushels per acre. Use the higher seeding rates for pure stands and the lower rates for mixed stands.
The other common annual species for beginners is buckwheat at 20 pounds per acre, which has been shown to take up large amounts of phosphorus and be beneficial to pollinators. Buckwheat should be mixed with one of the other cover crops due to its short life span. All three crops should be planted in late July. Other annual cover crops such as sorghum, millet, and sudangrass can be used just as a cover, but they produce higher residues to manage the following spring.
Most overwintering cover crops are not planted until fall except a few legume species. Legumes have the additional benefit of producing nitrogen. Red clover has long been used as a cover crop with wheat, but it needs to be planted in spring. Options for July seeding include cowpeas, crimson clover, and hairy vetch. Keeping your cover crop selection simple increases success rates and allows for better management in planting, timing and weed control. For successful cover cropping after wheat, start weed-free, and no-till the cover crops into soil moisture.
Next week we’ll take a close look at using oats as both a cover crop and forage.