MENOMONIE — Jason Cavadini’s work with cover crops as agronomist at the UW-Madison Marshfield Agricultural Research Station has turned up some unexpected findings.
Since 2014, Cavadini has been comparing no-till farming on plots using cover crops to plots without cover crops. What he’s finding, after taking measurements every two years using a soil penetrometer — often referred to as a compaction meter — is the top layer of soil on the plots where cover crops have been planted is firmer than the soil on the plots without cover crops.
And this is where referring to the soil penetrometer as a compaction meter can be misleading, Cavadini said, because while the soil in the plots using cover crops is firmer, water infiltration on those plots hasn’t showed signs of slowing.
“Basically the soil is getting firmer, but it’s not impeding water from getting through the profile,” Cavadini said Sept. 25 at the Red Cedar Demonstration Farm Fall Cover Crops Field Day in Menomonie.
So, while no-till practices go a long way toward improving soil quality, Cavadini said, if the goal is also reducing erosion, cover crops play an important role.
“We can improve soil a lot by reducing tillage, but improvements will stall out without continuous cover,” Cavadini said. “So to the question of why we are spending money trying to figure out how to put cover crops on the land successfully, it’s because if we want to take the next step when it comes to soil health, we have to figure out how to maximize cover.”
Cavadini has been integrating no-till and cover crops practices to support the Marshfield Agricultural Research Station’s dairy herd. He’s also been experimenting with interseeding cover crops between rows of corn.
“We’re trying to show we can have something growing between corn rows without sacrificing corn yields,” he said. “If we can cut tillage out and integrate cover crops into the system, and not do it at the expense of yield, then that’s a win.”
With the research station, Cavadini’s job involves trying to figure out how to reduce runoff from ag fields in the region, an effort he said will help improve public perception of the ag industry.
At the research station, Cavadini is looking at conservation practices like no-till planting, cover crops, use of perennials, taking less-productive acres out of production and putting livestock on the perennial acres.
The research, he said, can play an important role in reducing ag runoff in central Wisconsin. The research station is located in the Big Eau Plaine River watershed, which feeds into the Greater Wisconsin River watershed.
“The Big Eau Plaine and the entire Wisconsin River has the highest phosphorus concentration of all the tributaries,” Cavadini said. “One of the reasons for that is, if you look at the land use, Marathon County and Clark County will, on an annual basis, rank No. 1 and No. 2 in corn silage production and rank No. 1 and 2 in dairy production.
“What that means is, where you have corn silage, you have a two to three month period where all the land is covered and then all the sudden it’s bare, everything is harvested. Because it’s used in dairy situations, all that land is covered with manure, as well.”
Cavadini, who grazes a small herd of about 40 Black and Red Angus beef on his family’s 80-acre Cavern Point Farm near Stratford, has also seen success from the use of cover crops off the research station.
Cavadini transitioned his farm to no-till after buying the property six years ago, but he was still seeing erosion and ditching after significant rain events until he started using cover crops as well.
“The aggregate stability was still not very good,” he said. “Even though we stopped tilling, we still had erosion until we got it under perennial cover.”
Waterhemp a concern
The spread of waterhemp is a growing concern to Wisconsin farmers because the broadleaf can outcompete crops, germinate later in the season, requiring additional management, and has developed resistance to many herbicides, according to Tryston Beyrer, an agronomist for WinField United and a farmer in Dunn County.
“Waterhemp emerges later in the growing season. It usually starts to come out of the soil at the end of May, beginning of June, and it can extend all the way through August,” he said. “Even with the plants that are emerging in August, there’s not a good way to control the weeds, whether it’s herbicides or a thick canopy that’s going to shade it our or a cover crop to help suppress it.”
Waterhemp is dioecious, with male and female flowers on separate plants, leading to genetic diversity within a waterhemp population and allowing it to adapt to control tactics. Waterhemp has evolved resistance to six different classes of herbicides, Beyrer said.
He said there are a couple options to control waterhemp but the window is small and it can be difficult even if a plant hasn’t developed an herbicide resistance. Herbicide applications have to be thorough, and a single plant can produce more than a million seeds.
“One of the challenges of spraying this plant is you have to get very good coverage. Every branch has a growing point. If you miss any one, the plant can grow from that point,” he said. “To target your weed control optimally, the weed should be between 4 and 6 inches. The challenge is to scout for that and get timely weed control.”
Beyrer said waterhemp can grow up to 2 inches per day under optimal conditions.
“By the time it emerges, you’ve got three or four days before you start sacrificing your ability to control it,” he said. “And I’ve seen some reports where a 2-inch waterhemp plant emerged in August and still put on a seed head. It’s very prolific.”