Just when Sheldon Stevermer perfected his strip-till and fertility program, heavy June rain, and hail in 2014, have him rethinking his nitrogen plan. His family has strip-tilled highly variable soils for 11 years, leaving him confident that fall strips no longer needed a freshening pass in spring.
Strip-till has improved his soil structure to the point where it can manage extreme rains and heavy corn residue. “Three years ago, I realized I didn’t need to freshen the strips in the spring; crusting was no longer a problem,” says the Wells, Minn., farmer. “We no longer have washouts; our soil infiltration is much better, and our nutrient cycling has really improved.”
Stevermer's experimented with strip intercropping to gain 30-40 bushels per acre. His current row-spacing trials, still undercover, maximize yields through a sustainable and environmentally friendly approach.
But the extreme weather has refocused his attention. “I still think the biggest challenge is nitrogen application and the battle against adverse May-July weather,” says Stevermer, who farms with his brother Chuck. “Most experts want all the nitrogen on by V5, but we may need to make some changes based on what the weather’s dealt. For that to work, you have to get out there early, and you don’t want to lose it to a big rain.”
Stevermer has experimented with the balance between preplant nitrogen and sidedress over the years. In 2011, he was at 100% sidedress. He uses a 30-foot bar and Yetter Magnums with homemade pencil-stream injectors.
In the last few years, Stevermer has applied 40% to 50% nitrogen at planting, broadcast 25% to 30% over the top after planting and sidedressed the rest at V4-V5.
Although their soils hold heavy rains well, the extreme June weather in 2014 posed a serious nitrogen-placement and timing challenge. Stevermer injected 32% with a coulter in early June, but may have lost it in the rain that followed.
For now, he’s following trials comparing in-furrow 10-34-0 with 2 x 0 surface-banded nitrogen and sulfur to guide his planter-applied fertility decisions, which include the following:
- At planting, 40% of the season’s nitrogen (32% urea-ammonium nitrate) is applied. The rest is sidedressed at V4-V5.
- With a soybean-corn-corn rotation, the strip berm height is key to making fall strips work The strip-till depth was increased from 4 inches to 6-7 inches to get a 3-inch fall berm that doesn’t erode or become inverted over winter.
- The farm has transitioned from broadcasting phosphorus and potassium to variable-rate banding in 4.4-acre zones when stripping in the fall.
- Gypsum was added four years ago to build soil tilth and water infiltration.
- Balancing soil pH is very important.
Nitrogen and potassium cycling
Stevermer notes another key to strip-till success: understanding nitrogen and potassium cycling.
“Since we shift the nutrient return to the soil from early in the growing season the following year to later in the growing season, the growing crop could experience some nitrogen and potassium deficiency,” he says.
When residue from the previous year is tilled under, it breaks down very fast, releasing nitrogen and potassium into the soil to become available sooner to the new crop, Stevermer explains. Surface residue breaks down much more slowly through the current crop growing season, leaving fewer nutrients available to the plant until later in the season – especially with low-potassium soils, high-clay soils or soils with pH issues.
“If I had it to do over again, I’d increase my nitrogen and potassium rates going into strip-till to offset the residue tying it up,” Stevermer says. “Ridge tillers have battled the potassium-deficiency issue for a long time.”
A local seed dealer could not believe that the residue cover on Stevermer’s continuous corn fields had broken down so well. He has also experimented with various residue-management tools, such as sizing corn residue with a John Deere 1293 head equipped with Calmer BT choppers.
“We’ve tried various styles and brands of row cleaners; most work well enough if properly operated,” he says. “I like the Martin floating row cleaners that we added last year. After trying different closing wheels, we’ve seen the best results from standard rubber closers placed in the offset position. We’ve also tried narrow-gauge wheels on the planter. I like them in strip-till because of their narrow footprint.”
He practices controlled traffic as much as possible, with most equipment in 30- or 60-foot widths to reduce compaction.
The Stevermers began hiring out strip-tilling in 2003 after seeing the “unbelievable soil structure” of a long-time no-tiller. In 2005, they bought a Blu-Jet shank model with a mole knife. To dry out the fall strip in the spring, they added a 12-row Dawn coulter unit in 2007. When their soil structure improved and no longer crusted, that second spring pass became unnecessary.
But in the wet fall of 2009, “strip quality was terrible and we had trenches by spring,” Stevermer says. They dusted off the Dawn Pluribus to iron them out in spring. But they left some strips untouched, learning “that you could plant into some miserable fall-made strips, without a yield hit,” he says.
“It’s key to have the berm above the residue, because you can’t plant into a valley,” Stevermer says. That fall, they bought a new Krause continuous corn unit after testing it on some high-clay, high CEC soils. It provided just what they needed—a mound that doesn’t settle much.
“I became less concerned with a perfect black, residue-free strip and more concerned with making a good fall strip we could plant into the next spring,” He says. “We needed a strip-till unit with row cleaners that wouldn’t move soil with the residue.”
Stevermer recognizes that no one strip-till unit works on everything, and soil changes over time. “The fall of 2012 was really dry, and the fall strip produced some large clods in the wheel lanes from the spring 2012 planter pass. Those clods mellowed out pretty well by spring 2013,” he says.
While Stevermer is confident that they can plant into their fall strips without a freshening pass, he’s not 100% confident this gives them perfect planting performance. “We have some room for improvement on planting row unit ride and row unit down pressure,” he says.
When Stevermer quit freshening his strips in the spring, he moved that percent of nitrogen applied to the sidedress pass. However, he and his brother could tell their corn needed more nitrogen applied early. “We increased planter size and equipped it to dribble nitrogen off to the side of the row,” He says the past two years proved it to be a good move.