Cover crops get some northern exposure

Written by Jonathan Eisenthal

Stearns County Soil and Water Conservation District (SWCD) and University of Minnesota Extension recently hosted a field day at a 12-acre plot with different varieties of cover crops sown into corn and soybean fields near Roscoe, Minn. About 50 attendees — farmers, conservationists and educators — came on Wednesday, Oct. 30, to hear the experts talk about how cover crops really can work in Minnesota, and how they invigorate soil biology, hold topsoil, increase its water holding capacity and, under the right conditions and with careful management, can increase cash crop productivity.

A little rain at the right time helps too. Of course, the same goes for the cash crops.

Extension Educator Jodi DeJong-Hughes and SWCD conservationist Brad Wenz worked together with dairy farmer Dan Ley to set up the demonstration plot, which included rows of single varieties of such plants as winter rye, field pea, hairy vetch and purple-top turnip, as well rows where a “cocktail” of compatible species were all planted together into silage corn or soybeans.

Wenz spoke about a new precision web-based tool to help growers make decisions and quantify results, called the Nutrient Tracking Tool, or NTT.

The NTT was used for the demonstration plot, and the data show a 15 percent reduction in nitrogen movement where rye was planted — a potential for a savings of 212.82 lbs over the flat 12-acre site. The demonstration plot features a relatively shallow topsoil layer of Osakis and Regal loams (15-22 inches) followed by sand and light clay going down only about 50 feet where it reaches bedrock. Called a “surficial aquifer,” surface contaminants can reach the water table as quickly as a few hours. With that sensitivity, Wenz said, preventing nutrient loss is critical and cover crops can be part of the solution, he said.

Two methods were used for planting most of the cover crop species at the demonstration plot: no-till drill and broadcast incorporated. An additional two methods were tried for planting rye: slurry (the seed mixed right into the manure tank), and the least conventional — broadcast from an airplane. This approach can be patchy, unless the weather cooperates.

“We got an inch of rain a couple days after we did the aerial broadcast rye, and that made a big difference,” DeJong-Hughes said. “What I find with rye is that it’s pretty flexible. It can do a lot of different things and grow in a lot of different conditions.”

These cover crops will all be terminated in the spring, and a second field day at the Ley farm will demonstrate the variety of methods, including herbicide and mechanical means, for killing the cover and preparing the soil for spring planting of the cash crops.

Among the growing number of farmers who plant cover crops, those who raise beef or dairy cattle sometimes plant small grains and legumes as a winter cover that becomes a spring forage before planting begins for their corn or beans, according to Extension Educator Jill Sackett. She noted one particular farmer who insists on calving on winter rye.

“He’s only lost one calf to ‘scours’ since he started planting rye,” she said.

The plot was funded by Minnesota Corn Research & Promotion Council.

The experts conveyed the general wisdom that cover crops require management as intense as cash crops — noting exact variety and seed supplier used, date of planting, weather conditions –and to, in general start small and work up. Planting one cover crop allows the producer to get to know the species and how it works on the growers’ particular mix of soil, topography and climate.

With experience, many growers decide to go with a mixture. One of the key agronomic elements, dealing with the essential physics of agronomy, is that farmers with large-seed cash crops like corn and soybeans find success with smaller seed plants used for cover crops because the cover crop is often seeded into standing crops, to assure germination before a killing frost arrives.

“Diversity,” said Ley about how he favors mixtures of cover crop species. “If something isn’t working…tillage radish will die in the winter, but then I’ve got some annual rye that will keep growing in the spring.”

Ley has used cover crops for the past four years through USDA’s EQIP program, and he is looking forward to a second year working with SWCD and Extension to demonstrate the best species and agronomic methods to get a good cover crop into his rotation.

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