Don't let those fields sit idle. Use harvest as an excuse to improve your land for future use.
By Marilyn Thelen, Michigan State University Extension
With wheat harvest in many areas coming to a close, thousands of acres of ground will be left opened up. Leaving these fields idle until next spring may not be the best option. Here are several ways a farmer can utilize these acres to benefit their farming system.
Wheat stubble provides a mid-season land base for manure application. However, applying manure in the summer increases the risk of losing manure nutrients. Hot weather and surface application of manure increases the risk of losing ammonium-N. "Manure Application Method and Timing Effects on Emission of Ammonia and Nitrous Oxide," a June 2013 Michigan State University Extension publication, reported that with surface application of liquid dairy manure, 30 to 50 pounds per acre of Ammonia-N was lost within the first six to 12 hours after application. This represented 46 to 77 percent of the ammonia fraction. This loss was reduced 60 to 80 percent with immediate incorporation and over 90 percent with injection of manure. In addition to preserving nitrogen, this practice also decreases odor which can be a greater concern in the summer as neighbors’ may spend more time outside or have open windows.
In addition to nitrogen, manure is a good source of phosphorous and potassium. The long-time period between July and May increases the risk of nutrients being lost before another crop can use them. Cover crops and incorporation of manure are two practices that can work in concert to reduce runoff, leaching and volatilization of nutrients, all routes that nutrients take to leave the root zone.
Cover crops after wheat provide a growing crop to support soil organism, trap nutrients and reduce erosion. In fact, wheat is a good crop to follow with cover crops as it provides a longer growing period for cover crops to establish.
If you are looking for a cover crop that will winter-kill, some choices are oats, oilseed radish, sorghum-sudangrass or oats and oilseed radish seeded together. In addition to being terminated by freezing temperatures, oilseed radish and sorghum-sudangrass are excellent nitrogen scavengers and soil builders. Either would be a good choice to follow a manure application. All three provide protection against soil erosion.
Cover crops that will overwinter provide lasting residue and growth both above and below ground into the following spring are cereal rye, annual ryegrass and winter triticale. The concerns with these are they will need to be terminated in the spring and, as a result, can be more difficult to manage.
If manure is being applied to the wheat stubble, cover crop seed can be drilled, or we have seen good cereal rye stands when seed is spread after the manure application and incorporated with shallow vertical tillage or is slurry seeded with the manure. The picture shows a cereal rye stand just two and a half weeks after planted during a field demonstration using slurry seeding or vertical tillage to incorporate the manure and seed. Both slurry seeding with an incorporation attachment or shallow incorporation with a low disturbance tillage tool can reduce ammonia emission, however emissions may not be reduced as much as it would with a more aggressive incorporation method.
For additional information on cover crops, see the Michigan State University Extension article "Cover crop choices following winter wheat."