Cover crop research passes anecdotal stage

Ray Mueller
Now Media Group


Despite all of the attention given in recent years to growing cover crops and improving soil health in northeast Wisconsin, Shawano County Extension Service agriculture agent Jamie Patton suggests 'there are no answers yet' because relying on anecdotal findings is not sufficient.

Patton, who is a specialist in soil science and soil health, has been involved in numerous related cover crop projects and field days in the area during the past two years after arriving from Missouri. She and Winnebago County Extension Service agriculture agent Darrell McCauley reported on those activities at the 2016 grain crops production clinic.

Soil assessments

What's not in doubt is that much of the farmland soil in northeast Wisconsin falls short of the organic matter content that would allow better infiltration and storage of water and provide more natural sources of nutrition to crops, Patton stated.

Patton cited water infiltration studies by Andrew Docter of the University of Wisconsin-Green Bay which showed dramatic differences in water infiltration depending on the percentage of organic matter in the soil. In one test, a permanent vegetation site with 5 percent soil organic matter had a water infiltration rate of 10 inches per hour, while no-till soil with 2.3 percent organic matter could handle only 4 inches, she reported.

McCauley mentioned the December 13 and 14 rainfall of up to 3.5 inches in the Green Bay area which led to tremendous water runoff and soil erosion. Had cover crops been in place on the soil for the winter, the surface flow of water would have been reduced somewhat, he suggested.

Economic consequences

If farmers aren't concerned about the runoff as such, they might consider what a 6-inch difference in water retention could mean for a corn crop, Patton remarked. With those 6 inches representing about one quarter of the rainfall during the growing season, that could translate into about $150 per acre on corn yield.

Soil loss by erosion is also a blow to the bottom line. She cited findings that every ton of soil loss takes a toll of $7 in crop production. What's at stake with soil loss is the need for more inputs along with plant resiliency and crop yields and quality.

Regarding the drought in 2012, when Patton was still in Missouri, there were major differences in corn yield linked to how much organic matter and water storage capacity the soils had. Extreme weather events on both temperature and precipitation are predicted to become more common, she added.

Cover crop projects

In addition to the four operating farms on which several governmental agencies are conducting cover crop studies in northeast Wisconsin, Patton reported that a Sustainable Agriculture Research and Education grant is funding projects at six sites in Wisconsin. Two of those are near Angelica in Shawano County and Casco in Kewaunee County.

At Angelica, Patton supervised the seeding of plots of 40 pounds of oats with 4 pounds of radish per acre and another one with 60 pounds of barley per acre. Near the end of the growing season in 2015, they had 1.3 to 1.6 dry matter tons of foliage that could be harvested as feed.

Near Winneconne in Winnebago County, McCauley that cereal rye was aerial seeded on September 9 in standing corn — some of which was harvested for silage two weeks later while the remainder was taken later for grain.

Where the seeds germinated in the clay soil, the rye grew fast and the root growth was quite extensive, McCauley observed. Where the seeds did not germinate, the forces of nature served to collect it in batches.

Evaluations of cover crops

Based on her experiences in the area, Patton recommends radish varieties with small rather than large tubers, Crimson clover for its ability to supply nitrogen for the following crop and spring grains such as oats and barley because they will winterkill.

With winter wheat, Patton suggested the possibility of frost seeding red clover into the stand. Not only should the clover provide some control of weed growth both before and after the wheat is harvested, but it could grow vigorously in the latter half of the growing season and supply nitrogen for the next crop, she explained.

Among the cover crops she is familiar with, Patton has found that annual ryegrass establishes the largest root structure. But that also makes it difficult to eliminate the stand, she said.

Another practice which has caught Patton's attention is the interseeding of red clover into corn to be harvested for silage when the corn is at its V-4 to V6 growth stage in fields not having a serious weed problem. She explained that the red clover needs sunlight in its early growth stages because the seed provides energy for only about two weeks and that the clover will maintain itself at a certain stage before resuming growth once the corn is removed.

Among the downsides with cover crops are the difficulty of killing hairy vetch, the attraction that the foliage might be for slugs at moist sites, and the danger of armyworm infestations in the spring before foliage is removed and killed, Patton observed. She also mentioned the apparently different stances by the Natural Resources Conservation Service and the Risk Management Agency on the crop insurance eligibility for corn grown after the harvest of cereal rye in the spring.

Examining the roots

Growers of cover crops should not focus on or be misled by the amount of foliage growth above the ground, Patton emphasized. She's observed several instances where there has been extensive and depth root growth while the surface growth was minimal.

Those roots are very beneficial for soil microbes, adding organic matter, and improving water infiltration, Patton pointed out. She said that the plot near the school in Casco was an example of that.

Patton told the clinic attendees that she welcomes challenges to her observations and suggestions from farmers. She acknowledged that the time left in the growing season after the harvest of corn for grain or even for silage is often not enough for good growth of a cover crop.

To those who are concerned that the residual foliage of a cover crop would delay the warming of soil in the spring, Patton hopes that extended research will show that improving the soil health would address that concern. She said this is true because the soil heats faster than the water that it holds does.