Can cover crops and no-till work on irrigated land?
by Jonathan Eisenthal
Farmers across the Central Sands region of Minnesota are reacting with eager anticipation at the news that University of Minnesota Prof. Vasu Sharma is researching the use of cover crops and reduced tillage in an irrigation regimen. Will cover crops “steal” water from the cash crop in dry years, or preserve moisture? Will it reduce or prevent nitrate leaching? How will the change in cultivation impact yield? Will it prevent erosion of precious topsoil that lies atop the coarse, sandy soils typical of the central part of Minnesota?
The project is underwritten by funds from the Minnesota corn checkoff.
Sharma and her team planted cereal rye over field plots that offer side-by-side comparison of conventional and limited till methods.
They will get their first data in a three-year project following harvest in 2025.
“I have discussed this with many irrigators and they are very excited about it,” Sharma reports. “In fact, the Irrigators Association of Minnesota provided me with a letter (to help expand the project to a second location)….this research idea was proposed in Extension meetings I attended, because they don’t have any data on cover crop management in irrigated soils.”
Some growers in the Central Sands region tried cover crops in 2021, which then turned out to be the first in a series of drought years.
“Does the water used by cover crops have an impact on the development of the cash crop? So that was a big question back then,” Sharma said. “If so, what is that number? Or should we be growing cover crops in dry years, or not growing, or growing them only in wet years? So that’s why I came up with this idea. In our project, we have four irrigation scenarios, or we can say four climate scenarios, where we can put more water than what crop needs, we can put less water, we can put optimum water, or we can put no water. We will mimic those climate scenarios and see how these cover crops and no-till practices impact our crop yield, irrigation requirement, and nitrate leaching.”
The project will compare the use of a 12-inch ripper for conventional tillage, versus no-till. They will follow a corn-soybean rotation throughout the three years of the project. A key issue for growers who use irrigation is that their fields are not always a single soil texture. There may be areas of clay soil amongst fields with sandy soil. Many of these growers already balance the application of irrigation water with the potential for ponding when water runs to low spots with denser clay soils. They are eager to see if cover crops can help.
Sharma believes this area of investigation will continue and grow beyond the scope of this first project, because of the potential for conservation techniques to solve problems that irrigation users encounter in their quest to grow the most food they can, with the lowest environmental impact.
