Cover crop conversations are everywhere these days, but making them work can be tricky.
Bill and Ty Rohloff, who run a 1,200-acre grain farm near Fort Atkinson, have been practicing no-till on most of their farm since the 1980s, and now they are also utilizing cover crops to build soil and prevent erosion.
When the family hosted the Discovery Farms field day last week, Bill Rohloff said, “Our goal has always been to leave the soil in better shape than when we started.”
The no-till and cover crops are a part of attaining that goal. They also have established buffer strips in fragile areas near streams, and they are participating in a nitrogen study carried out by the Discovery Farms program.
In the field, participants saw tillage radishes and turnips beginning to emerge among annual rye grass. The tender plants were popping through a ground cover of chopped straw from a harvested wheat field.
“These plants were drilled in two weeks ago onto a harvested wheat field," Ty said. "All of this will grow and cover the ground before it freezes and will be rotted down before spring.
“It’s really a good soil builder.”
Cover crops reduce wind and water erosion; reduce nitrate leaching and export from tile drains; and reduce phosphorus runoff. Many, many studies across the Midwest have shown this.
Matt Ruark, cover crop specialist with the University of Wisconsin-Extension, said the cover crop selection depends on the goal.
He pointed out that the radish alone or in a mixture establishes well when planted by early September. Radish winterkills and decomposes quickly, which may be why it is difficult to determine the exact nitrogen credit. The deep roots, however, are the real benefit because they bring minerals from far below to the soil surface, where they will benefit crops. They also tend to aerate the soil.
Grasses are ideal for soil erosion control.
Options when utilizing covers
Ruark said farmers considering a cover crop plan have two options.
One is to frost seed red clover into winter wheat in spring, and as soon as the wheat comes off and light hits the field, the red clover takes off.
“You can get 40-60 pounds of nitrogen credit with this and can grow a lot of nitrogen when you terminate the crop late in fall,” he said. “We have seen yield increases on the grain farms because we have established a legume in the middle.”
A second option is establishment of Berseen and crimson clover after harvested wheat.
“There is a lot of nitrogen in the biomass," Ruark said. "The advantage to this is they will winter kill so you do not need to terminate it in fall.”
This was tried one year and resulted in a yield bump but not a nitrogen credit. He pointed out that it is a part of an ongoing study, and they are just beginning to build a data base of results.
Ruark pointed out that his work is primarily with dairy farms where the straw has been removed. On farms like the Rohloffs' where straw is chopped back on the field, it is possible that the nitrogen can be tied up in the straw. It is unclear which system works best yet.
Heidi Johnson, Dane County UW-Extension, told the field-day attendees she does not recommend planting radishes as a cover without the inclusion of grass. She said it may be beneficial, however, when planted into chopped wheat straw.
Ruark and Johnson said they are playing around with experiments interseeding a cover into corn. They said radish and clover could get some nitrogen into continuous corn systems, but grasses do not do as well for this.
Ruark pointed out that when establishing cover crops in corn systems, it will be important to consider herbicide usage.
The University of Wisconsin Extension has a new cover crops website for those interested in learning more about what would work for specific conditions: fyi.uwex.edu/covercrop.