State urges Minnesota farmers to plant more vegetative cover to fight nitrate contamination

Hemp, hazelnuts, oats, turnips, alfalfa, Kernza … there's a sizable menu of plants to grow for vegetative cover in fields, but much more needs to be done to protect the state's soil and groundwater from contamination by nitrogen fertilizer.

That's the upshot of a new report on vegetative cover in Minnesota released by the state Department of Agriculture. It comes as the state fights a nitrate contamination crisis linked to commercial fertilizers and overuse of manure on traditional row crops of corn and soybeans.

"Increasing vegetative ground cover is an important strategy to help protect water and soil resources," the authors said.

An appendix of the report includes links to more than a dozen grant and loan programs farmers can tap for help exploring new practices.

Researchers surveyed farmers and industry professionals in three parts of the state where the groundwater is highly vulnerable to nitrate contamination: the southeast, southwest and central sands area. Drinking water with elevated levels of nitrate has been linked to potentially serious health problems, particularly for infants younger than 6 months.

In an effort to improve water quality, the state agency is urging farmers to try to replace traditional row crops of corn and soybeans with perennials that don't require tilling, for example, or to grow different plants offseason so they keep vegetation on the ground. Bare soil is vulnerable not only to erosion, but also to farm chemicals leaching into groundwater and drinking-water wells.

There's a range of perennials and cover crops promoted for use as forage for grazing animals, cash crops if markets are better developed or simple cover for the ground offseason. They include annual oilseeds such as winter camelina and pennycress; root vegetables such as turnips and radishes; and small grains such as triticale, sorghum and oats for animal feed and food.

The University of Minnesota is developing other specialty crops such as hazelnuts, perennial sunflowers and an oilseed called silphium. Meanwhile, Kernza, a new type of versatile perennial wheatgrass, as well as camelina and pennycress "are being ramped up to field scale," the report said.

Kernza has been shown to cut nitrate leaching into groundwater, with its long root system.

Cover crops are "gaining traction" in the three areas, the report said, but still is grown on only 2 to 8% of the cropland in those three regions. Nearly three-quarters of the state's cropland is planted with corn and soybeans, a monoculture that requires heavy chemical use and can leave the soil bare over winter.

The report notes that the increase in small craft brewing could increase demand for locally grown malting barley. Likewise, there's a growing market for pet food for small herbivores, it said, such as guinea pigs who thrive on timothy grass.

There are plenty of obstacles. For example, the report notes supply chain bottlenecks of equipment to cultivate and harvest alternative crops to corn and soybeans. And farmers need to know there's a buyer for their product or they are less likely to plant alternatives. Minnesota's short growing season also presents a challenge.

Jennifer Bjorhus • 612-673-4683