Like a lot of farmers, Curt Ferris has wrestled with large amounts of crop residue in corn-on-corn fields. He invested in a stalk chopper and a deep ripper to improve conditions for a good corn stand in the spring.
But getting a good stand continued to challenge his Iowa Falls farm, which is roughly 75% corn-on-corn.
“I had a real problem with crop residue,” says Ferris. “This genetically engineered corn just doesn’t break down. It’s tough.”
Two years ago he began an experiment that side-lined the deep ripper. Instead, he removes about half the corn residue after harvest, with no tillage until spring.
Stopped fall tillage
“I have very good results with it after two years,” he says. “This year, instead of using a deep ripper, I field cultivated in the spring. I had a beautiful stand. I am really excited about it.”
A big yield bump that showed up in strip trials on his farm in 2014 undergirds that excitement.
Ferris embarked on his residue-removal experiment after signing on with DuPont to supply stover for its new cellulosic ethanol plant in Nevada, Iowa, coming on-line in late 2015. One of several hundred farmers working with DuPont, he hoped that partially removing stover would allow him to reduce tillage and still give the following corn crop a good start.
“There were a lot of exciting new areas we could explore with tillage, planting practices and yields if this worked out,” says Ferris.
After harvesting strip trials on his farm in 2014, he concluded he may have hit the trifecta of higher yields, lower costs and better soil conservation from less tillage.
“In 2014, the corn came up quicker where part of the residue had been removed, maybe four to five days,” he recalls. “All through the season it was taller and looked better. And it yielded 10 bushels/acre better. If this continues, corn-on-corn yields will be even with corn after soybeans. This is huge.”
Ferris’ yield results are well within the range of results from three years of strip trials conducted by the company, says Frank Rydl, a DuPont Pioneer agronomist. “On average over three seasons, we are at a 4.9 bushel/acre yield advantage, with a nearly 90% win ratio,” he says.
Trials have compared grain yield between strips of no residue removal versus 50% removal. A typical 190-bushel/acre crop produces 4.5 tons/acre of residue, and the DuPont harvest crews removed almost half that to compare. The strips are tilled to produce typical non-stover-harvested seedbeds that encourage fast, even emergence.
The remaining residue – 2.25-2.5 tons/acre – is DuPont’s target for its partial stover removal program. It is based on USDA data on the soil cover needed to protect relatively flat soils in the program from erosion, while also maintaining organic matter. That assumes use of conservation tillage systems in continuous corn.
“What we have seen with partial stover harvest is more uniform stover across the field, resulting in more even stands,” says John Pieper, who heads the cellulosic feedstock supply chain development program for the ethanol facility. This is a result of removal practices that seek to leave the same amount of crop residue on high- and low-yielding parts of fields. This reduces the likelihood of over-tilling parts of a field, a common occurrence where yield and resulting residue often varies widely within a field, he says.
Long term, as more cellulosic ethanol plants are built, and new enzymes are possibly developed to enhance livestock feed value of corn stover, more farmers could benefit from partial residue removal, he adds. This could enhance yields and reduce tillage needs as overall residue loads continue to climb as grain yields increase.
Mellower soil, lower costs
“This turns your corn-on-corn ground into a field like you raised soybeans on it,” says Brian Sampson, Roland, Iowa, who also is in the second year of the residue-removal program. “The ground is so much more mellow, especially if you don’t till it in the fall. The seedbed is excellent and the crop comes up better.”
That saves an estimated $15-25/acre by eliminating fall deep tillage. And yields may be higher, though Sampson hasn’t confirmed that with strip tests.
Ferris estimates his fall tillage savings at $20/a. His payment for about 2 tons/acre of stover nets an extra $30/acre, plus the value of extra yield. Since he has access to hog manure at the cost of hauling, he avoids the estimated $18-22/acre cost of replacing phosphorus and potassium contained in the removed stover.
Like Sampson, he’s taking a watch and wait approach to the number of years he’ll consider partial stover removal from each field, which DuPont suggests at three out of four years in continuous corn. He’s also wary of taking too much stover from fields that are more erosive.
“There is some ground that may not be suitable,” he says. “On more erosive fields, we took off less residue. Controlling erosion is critical.”