Multi-species cover crops get more popular with awareness, incentives
Still a pretty small piece of the cover crop pie, planting multi-species mixes is increasing in the Delmarva region as researchers and farmers gain a better understanding about their use.
Using mixes combines different modes of action for added benefit to a cropping system and the environment, advocates say, keeping more nutrients from leaving the field.
A commonly-promoted mix is to combine a brassica like forage radish to scavenge nutrients for the coming corn or soybean crop and alleviate soil compaction; a cereal grain for biomass production to suppress weeds and a legume for nitrogen fixation.
But as more information comes out through research and workshops, and with help from state and federal programs incentivizing the use of mixes, more farmers are experimenting on their own to see what works best in their operation.
In Delaware, the Sussex County Conservation District has advocated the use of cover crop mixes through its air seeder pilot program which allows for earlier planting into standing cash crops and only seeds mixes, and through workshops and field days focused on soil health. The percentage of total mixes in the district’s cover crop program increased ten percent from 2016 to 2017 and up almost 20 percent from 2012, according to district data.
“It’s certainly gotten more popular here in Sussex County,” said Debbie Absher, the Sussex Conservation District’s director of agricultural programs. “We’ve been talking about mixes and people are starting to experiment with their own mixes.”
This year, acreage in the air seeder pilot program was down slightly, perhaps due to crop rotations, she said, and also it was the first year the district charged a fee for using the seeder.
“We’ve had several people say they’d wish they’d done it this year so I think they’ll be back,” Absher said.
With an incentive for early planting and a new eligibility for three-waymixes, data from the Maryland Cover Crop Program shows a steep increase in acres planted with a cover crop mix. In 2017, 7,628.7 acres in the program had a mix planted and in 2018, acres including legume mixes, radish mixes and cereal mixes rose 67.7 percent to 12,798.8. Of the 2018 mix acres in the program, 2,834 acres had a three-way mix, according to the Maryland Department of Agriculture. Statewide, Maryland farmers signed up more than 639,000 acres in the program.
On his family’s Kings Grant Farm in Chestertown, Md., Webb Johnson was fairly early in using cover crop mixes to buiid soil quality, reduce fertilizer and herbicide inputs and increase yields. Johnson, who also sells cover crop seed, said by integrating cover crop mixes into their soybean production scheme over several years, he’s seen a ten bushel per acre increase.
“It’s not like a one-year thing,” Johnson said of the benefits. “You’re not going to see it overnight.”
Participating in cover crop research for years, Johnson is now partnering with the University of Maryland in the first year of a research project led by Dr. Ray Weil, quantifying the nutrient-saving benefits of mixed stand cover crops.
Along with multiple sites at the university’s Beltsville Research Farm, Johnson and four other Eastern Shore farmers applied a mix consisting of a brassica, a cereal grain and a legume into a standing corn or soybean crop on half of a field and then planted the mix after harvesting the cash crop on the other half for comparison.
The farmers are also asked to kill the cover crop later in the spring or plant their next cash crop directly into the live cover crop stands, according to Nathan Sedghi, a doctoral student in the university’s Department of Environmental Science and Technology working on the research.
Sedghi said they expect to repeat the cover crop trials two more years, gathering data on nutrient movement through leaching and runoff.
For the last three years, Dr. Mark Reiter, Virginia Tech associate professor of soils and nutrient management, and doctoral student Bethany Wolters have been testing different cover crop mixes on the Eastern Shore of Virginia.
“There’s a lot of farmers interested in mixes and a lot of interest in letting them grow longer,” Reiter said.
Studying mixes of three and four different crops and one “kitchen sink mix” of nine different crops, Reiter said under stressed conditions, the mixes in the study produced more biomass than a single cover crop and biomass production was highly correlated to the cover crop’s nitrogen accumulation.
Mixes that included a legume had the best yield benefit on following corn corps than mixes without, Reiter added.
With support from the USDA Conservation Innovation Grant program, Reiter plans to repeat the same treatments for at least three more years.
“I think it’s a good demonstration of how important they can be and how useful they can be,” Reiter said.
Even with their usefulness, there can still be management issues. Insect damage was an issue in the nine-way treatment in his study, suggesting it’s possible to have too many species in one mix.
“I think the lesson there is when you change the system you need to have a good handle on all the things you’re changing,” Reiter said.
Johnson said, like any other farming tool, it takes planning and management to get the most out of cover crop mixes.
“When you’re cover cropping, you’re thinking about the next year’s crop,” he said. “You really have to sit down and do you’re homework on what you want to plant and not just go throw it out there. There’s a mix for everything, one way shape or form.”
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