Testing soil-nutrient levels with modern technology reduces inputs and boosts corn yields for Minnesota strip-tiller David Legvold.
By Jack Zemlicka, Technology Editor
Gathering and analyzing data on soil health is gradually becoming an integral part of how strip-tillers operate to become better long-term stewards of their land.
But without the right guidance or know-how, there’s little advantage to be gained.
Minnesota’s David Legvold considers himself lucky to have gotten exposure to the benefits of onfarm research after he began strip-tilling 9 years ago. Through work with educators in the state, and his own ambition, Legvold has reduced input costs, boosted yields and refined his farming philosophy to focus on prolonged soil health.
The combination of strip-till and research is paying off for Legvold, whose corn yields have increased by 10 to 20 bushels per acre during the last 5 years. Last year, he says he was pushing 300 bushels per acre in some areas, based on his yield monitor, and is consistently in the 270- to 280-bushel-per-acre range.
“So many farmers are afraid of leaving bushels in the field, but I’m also concerned about leaving dollars in the field,” he says. “Bushels are one thing, but if I leave excess nitrogen or fertilizer in my field, then I’m leaving money in the field.”
Focus On Fertility
BENEATH THE SOIL. Since adopting strip-till 9 years ago, Minnesota’s David Legvold has focused on analyzing and improving soil health through extensive soil testing and use of technology like lysimeters to track nitrogen loss beneath corn plants.
When Legvold first started strip-tilling corn, after years of no-tilling, he says he paid more attention to soil texture, rather than nutrient contents. But for the last 6 years, he’s worked with St. Olaf College, located minutes from his farm in Northfield, Minn., to place more of an emphasis on analyzing and improving soil health.
Through this partnership, Legvold has “tinkered” with nitrogen application rates in strip-tilled cornfields farmed by St. Olaf students, along with his own 500 acres of corn, and been able to reduce fertilizer application by a third through zone application.
“I used to slam my nitrogen on all on at once in the fall. Now we can do it in 2 or 3 shots,” he says. “I can still put some on the fall, although I resist fall application like the plague because I don’t want to lose those nutrients in the field.”
He may band 8 to 10 pounds per acre of monoammonium phosphate (MAP) and diammonium phosphate (DAP). But after years of strip-tilling Legvold typically has 40 pounds per acre of residual nitrogen built up on soybean ground going into corn. This allows him to scale back nitrogen application in the spring.
He typically applies 40 pounds per acre of banded urea in the spring with his 12-row Environmental Tillage Systems Soil Warrior when he freshens the fall strips. This spring, the weather didn’t allow Legvold to take his strip-till rig back in the field, so he applied 40 pounds of 28% liquid nitrogen with his John Deere planter.
“Because I have single disc openers, they’ll put fertilizer into blacktop if you want them to, and I can get it in a 3-by-3 inch configuration,” he says. “That keeps the liquid nitrogen far enough away from the seed so it’s not going to bother anything.”
Legvold will then sidedress the balance of nitrogen with a custom unit. Amounts range from zero to 120 pounds per acre, depending on the overall recommendation generated by the Iowa State Corn Nitrogen Rate Calculator.
Legvold swears by the application tool to generate best-management practices (BMP) for nitrogen rates. He admits farmers are often surprised at how little nitrogen he applies in the fall, but with multiple “spoon feedings” during the growing season, efficiency is the goal.
“Every year for about 5 years, we’ve found that where we’ve exceeded the maximum curve of the Iowa State nitrogen calculator, profitability goes down,” Legvold says. “Sticking to that rate has been the most economically beneficial.
DATA DRIVEN FARMING. In conjunction with St. Olaf’s College, Legvold has cut fertilizer application by one-third and improved corn yields to near 300 bushels per acre in some fields through strip-till and on-farm research.
“Before we started working with the college, I never had thought about that data.”
Probing For Improvement
Another decision-making tool introduced on Legvold’s farm in the last year is a soil lysimeter that measures nitrogen levels beneath corn plants.
A 4-foot-long tube, with a semi-permeable ceramic end, is inserted below the roots and vacuum pressure pulls up a sample of ground water, which is analyzed to determine how much nitrogen has passed the plant.
Based on initial testing during last growing season, Legvold is finding that he’s losing nitrogen in over-applied areas.
“When that nitrogen is 3 feet down, some corn roots will get at it, but it’s still well below where it should be,” he says. “I think this research opens doors for us to use slower-release nitrogen in the upper soil zone to avoid loss.
“East of us, where it’s really sandy, nitrates travel willingly, and those farmers have begun to use lysimeters. So I think there’s a lot of potential for us as well to find out where we’re losing nitrogen.”
St. Olaf students are also working with Legvold on macro-invertebrate analysis in the field to do aggregate stability testing of soil permeability. Both the college’s test plots and Legvold’s fields have seen organic matter increase from the 1.9 to 2.5 range to the upper 3 to lower 4 range during the last few years.
Last year, Legvold and students conducted a macro-invertebrate analysis of a conventionally tilled plot with one that was strip-tilled. After a soaking rain, samples were taken from the fields and Legvold and the students also examined the surfaces of each plot.
“We walked on the middles and everything was fine. Then I heard this squealing and laughing because a couple of students had walked onto the conventionally-tilled field and were in 6 inches of pudding,” Legvold says. “Their boots had gotten sucked off. The difference in soil quality was amazing because water penetrated the strip-till plot pretty well. The other field was goop.”
SPOON FEEDING NUTRIENTS. Legvold applies only a small amount of nitrogen in his fall strips and applies 40 pounds per acre of banded urea with his 12-row strip-till unit in spring. He then sidedresses the balance with a custom rig, according to the Iowa State Corn Nitrogen Rate Calculator recommendation.
After several years of examining and testing soil health, Legvold decided to take a closer look underneath the soil surface.
In 2012, he hosted a research group from the Minnesota Association of Soil Scientists, who dug a 5-foot-deep soil pit in his cornfield to examine soil structure. A soil scientist from the National Resources Conservation Service (NRCS) also visited and compared Legvold’s strip-tilled land to another conventionally-tilled plot he recently began renting.
“In my field she found worm holes that were probably 4½ feet deep, about the diameter of a pencil. She pointed out that the lining of the holes was black and thick,” Legvold says. “That’s the organic matter that those worms hauled down into the soil. I’m seeing these nuances of soil quality and soil health, that’s hard for me to get my head around.”
Legvold has begun to work with several other new strip-tillers in the area, sharing what he’s learned from onfarm research and how it’s improved his overall operation.
The goal is to get them on board at an early stage with adopting data collection practices that will sustain their soil health, long-term.
“I’ve learned quite a bit and now my job is to help other farmers who want to try strip-tilling. I’ve probably got 3 or 4 others who I’m going to do a little strip-till for,” Legvold says. “In some cases, I say, ‘I think you’ll like this, I’ll come over and do it for nothing this year.’
“It makes me feel good, it makes them suspicious and that’s a good thing.”