Cover crops provide armor for the soil to sequester nutrients and hold them for availability to subsequent crops, preventing those input nutrients from leaching into groundwater.
At a Bazile Groundwater Management Area cover crops field day near Creighton, Neb., last September, Dan Gillespie, Natural Resources Conservation Service no-till specialist, told participants that cover crops can dramatically increase water infiltration into the soil profile, further reducing runoff and leaching. This is increasingly important in areas where sandier soils make nitrate leaching more of a problem.
In the 1980s, an area in northeast Nebraska that was experiencing increasing concentrations of nitrates in groundwater came to be known as the Bazile Triangle, within the watershed of Bazile Creek. This was especially troubling, because the wells of several rural communities and farms, impacting more than 7,000 residents, were being affected.
To mitigate and reverse this trend, numerous voluntary programs were implemented by producers, in cooperation with several agencies, spearheaded by the Lewis and Clark Natural Resources District.
In 2016, a Bazile Groundwater Management Area was designated, expanding the original "Triangle" to cover four NRDs, three counties, 21 townships and 10 rural communities. A mitigation plan for the area was recognized nationally as the first to address nonpoint source pollution.
Today, Bazile GMA cooperators and partner agencies continue to research proven methods to use nitrogen more efficiently to prevent leaching and reverse concentrations.
At the Jim Fuchtman farm south of Creighton, more than 100 producers, cooperators and partner agency staff members gathered last fall to demonstrate cover crop seeding into standing corn with a Hagie high-clearance machine retrofitted with a Montag bulk tank and blower unit that meters cover crop seed out to the boom of the high-clearance machine.
Other cooperators on the demonstration project included Albert Friedrich, Plainview, and Carpenter Farms at Creighton. Garrett Carpenter, who is a co-owner of Midwest Seeds where the field day was hosted, farms with his father, Mark, and uncle Scott.
Gillespie noted during the field day that it is challenging for farmers to keep a living root in the soil as much as possible during the year. "Seeding rye into standing corn is an insurance policy that none of the nitrates you put on will leach into the groundwater," Gillespie said. "Cover crops suppress the germination of weeds and help to enhance water infiltration. You are able to catch it, store it and use it, and this happens repeatedly through the year."
Fuchtman noted that he has tried both aerial seeding and high-clearance machines for seeding cover crops since 2015. While he hasn't observed a dramatic increase in organic matter yet, he is optimistic about the results. Fuchtman tries to slowly feed nutrients to his corn crop throughout the year, to reduce the chances of leaching.
He told the group that he applies about 1.1 pounds of nitrogen per expected bushel per acre yield, which is about 250 bushels per acre on the demonstration site. He adds nitrogen as a liquid starter, followed by a dry application in mid-June, with a nitrogen stabilizer. The rest is fed to the crop through fertigation with his center pivot.
"We try to have the crop utilize every pound of nitrogen we put on," Fuchtman said. "According to our soil tests, we have no residual nitrogen."
While both aerial and high-clearance seeding work for cover crops, there are considerations for both methods. Gillespie suggested that aerial seeding may have to take place earlier in the season, before the crop canopy becomes too dense to allow the seed to reach the soil. Selecting corn hybrids with more upright leaves may also enhance germination when cover crops are aerial applied.
The Hagie unit used in the demonstration had drops that are 1.25-1.5 inches long. An advantage of the high-clearance system is that it gets the seed through the drops and on the soil, reaching through the canopy.
The seeding system can blend two different seed types, such as rye and brassica seed. At the Fuchtman site, about 64 pounds per acre of cover crop seed were applied, including 60 pounds of cereal rye per acre and 2 pounds per acre of radish and 2 pounds of turnips.
"The seeding went well at the demonstrations sites we had last fall," says Jeremy Milander, Bazile GMA Nebraska Extension agronomist. "Within a few days of seeding, we saw germination, and the cover crop was established at the time of harvest. This spring, the cover crops were a little slow to take off, compared to some years, but around mid- to late-April, they really took off and we had excellent establishment."
"A high-clearance seeder has the advantage of being able to seed before harvest, allowing for earlier germination and growth, compared to postharvest drilling," Milander explains. "The use of a high-clearance unit also eliminates some of the seed loss and drift that may occur with aerial seeding."
Milander says that establishing cover crops is one crucial best management practice that can help with nitrate leaching issues. "Planting cover crops can take up some of the excess nitrogen left over from the corn crop after fall harvest," he says. "The nitrogen will be tied up in the plant during the offseason, which is when a lot of leaching has been found to occur."
The demonstrations continued into this growing season. "We are working on another set of demonstration plots in which we are seeding cereal rye and a cereal rye-vetch mixture at three different times," Milander says. "The first seeding date was done during the vegetative stages. Another broadcast seeding would be done around early September, similar to what we did with the Hagie machine last year. Lastly, we will be drilling postharvest."
Cost-share funding is available for producers within the Bazile GMA to help them implement cover crops and other nitrate management practices. A producer in the GMA must have a contract for cost-share assistance through the NRCS Environmental Quality Incentives Program, with funding available through a general pool and through special initiatives like this.
"The Bazile GMA has been elected as a National Water Quality Incentive area," says GMA coordinator Connor Baldwin. "What that means is the producers within the GMA get put into a separate pool other than the general NRD fund pool. In that pool, we mainly focus on practices such as cover crops, nutrient management and irrigation water management, among other practices that combat nitrate issues we have inside the area."