Weeds are nature's way to try to heal problems with the soil but with conventional agricultural practices 'we don't allow them' to do that, northeast Wisconsin farm demonstration project manager Brent Petersen said.
Petersen, who is based at the Brown County land and water conservation department, doesn't advocate letting weeds take over the healing of soil health problems. Instead, he proposes that more farmers begin to grow late season cover crops to address that problem and to obtain several other benefits such as livestock feed and a natural source of nitrogen for subsequent crops.
That message was delivered by Petersen in a presentation to attendees at the Calumet Council Forage Council's summer twilight meeting at custom cropping operator Greg Vollmer's machine shed. He summarized the projects and results that have been carried on four farms in Brown and Outagamie counties that are formally enrolled in the project and on others that have cooperated with it.
Funding for that multiyear project is provided mainly by the Great Lakes Commission, which is endeavoring to protect and improve the surface water quality in the basins which are connected with the Great Lakes, Petersen noted. He said the basic problem with pollution of waters in those bodies of water is not runoff but the failure of infiltration of water on the land from which runoff occurs — a phenomenon closely tied to both soil structure and whether the soil is covered by vegetation during rainfall.
Describing the challenge
In Petersen's view, there is too much tillage of agricultural land, too much soil compaction from surface traffic, and not matter organic matter in the soil to keep it loose and able to store more water. He indicated that soil organic matter — at less than 3 percent in many cases — is less that half of what it was before the land was converted into continuous agricultural production.
'Compared to nature, soil tillage is a catastrophic event,' Petersen remarked. 'Soils are much more delicate than we realize.' He pointed out how woodlands, prairies, and other non-tilled areas on the landscape have survived for hundreds and thousands of years on their own.
Tillage not only destroys existing soil structure but it also allows oxygen to enter the soil, thereby accommodating the destruction of organic matter. He said that every one percentage point increase in soil organic matter also provides an additional 30 to 40 pounds of available nitrogen per acre.
While the major agricultural crops grown in the area are green for six months or less, there are another six months of the year during which other crops — popularly known as cover crops — could be grown to use the sunlight, greatly extend the time when there are live roots in the soil and to support the beneficial soil microbes, bacteria and fungi that promote soil health, Petersen advised.
Dealing with excuses
During his time with the demonstration project, Petersen has become acquainted with many excuses on why such an approach is difficult or impossible. That list includes concerns about time and money, about whether other crops would grow well late in the season and the belief that having a nutrient management plan is sufficient for protecting water quality and promoting soil health.
But there are clovers, grain species, and grasses that can be grown successfully in the region as cover crops, Petersen stated. Having living plants in the soil for longer periods increases the amount of sugars that are exuded into the soil to support a variety of biological processes.
Cover crops also reduce extremes in soil temperatures, thereby saving moisture for other plants, and limiting the mortality of soil bacteria, Petersen pointed out. When living roots are present, the population of beneficial microbes can increase by multiples of 1,000 to 2,000. He also noted how earthworms thrive in the presence of more organic matter and contribute to soil health.
Popular cover crops
Petersen reviewed the findings from cover crops such as barley, radish, crimson, Berseem and red clovers, rapeseed, oats, Austrian peas and combinations of them. Other choices that serve much the same purpose but that also lend themselves to harvest for livestock feed are triticale and winter rye (the only two species for which a planting after October 1 is appropriate).
At several of the sites, comparisons were made with conventional practices or with land belonging to adjacent nonparticipating owners. One situation which caught Petersen's attention was the dramatic difference in the volume and color of runoff water following a 3.5-inch rainfall on December 13, 2015 in parts of Brown County.
Other factors and variables which are being tried and evaluated are the timing of seeding, interseeding in standing crops, liquid manure application methods and rates, no-till seeding, disk openers, row closing wheels, the effect of herbicides, nitrogen applications and the equipment for handling those tasks in order to have minimal disturbance of the soil, Petersen reported.
The original four farms in the demonstration project are Dan Brick's Brickstead Dairy east of Greenleaf, Tinedale Farms at Wrightstown, Greg Nettekoven near Black Creek in central Outagamie County and Van Wychen Farms near De Pere.
Joining the project more recently have been New Horizon Dairy (Dave Vande Hey) and Vande Wettering Farms. Data has also been collected on the Wiese Brothers farm near Greenleaf. A related project is the paired watershed runoff site along Lost Dauphin Road near the Fox River southwest of De Pere.
Petersen urges other farmers to undertake small scale cover crop ventures in order to make their own observations and comparisons. Following decades of farming practice that haven't always been friendly to soil structure and health, his message to farmers today is that 'we don't have grandpa's ground any more.'
Petersen can be reached by email at Petersen_BA@co.brown.wi.us or by phone at 920-391-4643 or 920-606-3068.