For Minnesota growers Kevin and Larry Lahr, strip-tillage is one more precision farming tool. The Lahrs' recent switch to strip-till is part of their long-range strategy to “micromanage every field,” Kevin Lahr says. “Strip-till fits into our goals for precision farming. We want to be able to put our fertilizer and seed dollars where they will earn the maximum return. For us, the main focus is on variable rates. It just happens to come in strip-till form.”

Kevin and his father Larry grow corn and soybeans on 1,700 acres of rolling, variable terrain near Sauk Centre, in central Minnesota. They've been yield mapping since 1996 and have soil sampled the entire farm in 2.5-acre geo-referenced grids. They've also tiled most of their land, setting the stage for reduced tillage.

Their soil test data, combined with yield and elevation maps, showed nutrient surpluses on lower-yielding hillsides, while higher-yielding bottomlands were short of nutrients. They were eager to begin variable-rate fertilizing, so when John Deere (JD) introduced the 2510S strip-till machine in 2008, they decided the time was right to integrate their fertility and tillage programs.

Strip-tillage is a natural fit with variable-rate management, says Centrol Crop Consultant Brent Werven, Villard, MN, who has worked with the Lahrs for 18 years. “Our goal is to create a repeatable zone or band of higher fertility, using less tillage, instead of trying to bring the entire field up,” he says.

THE LAHRS' 40-FT. strip-till machine with 30-in. row spacing matches their 16-row Deere planter. Tillage shanks fitted with fertilizer injection tubes lift and loosen a 10-in.-wide strip of soil while applying anhydrous ammonia and dry fertilizer in a band about 6 in. deep. The soil between the strips is left undisturbed. Dry fertilizer is delivered with a JD Commodity Air Cart, with three bins for phosphate, potash and micronutrients. Nutrients are blended on the go according to prescription maps.

The rig plus anhydrous ammonia tank is pulled by a JD 9630 tractor. Making it all work is JD's real-time kinematic (RTK) guidance system with GreenStar 2 software.

In fall 2008, the Lahrs strip-till-ed 700 acres of harvested soybean ground that was going into corn the following spring, and 50 acres of corn ground going into soybeans.

The first season was definitely a learning year, Kevin says. Compared to pulling a 22-ft. disk ripper, “strip-till is much more difficult and demanding.” Adjusting the strip-tiller for different soil conditions is key, he found. “You have to fine-tune it for every field. I'd go a ways down the field, get out, check it, make adjustments, go a little farther, get out and check it again.”

The row cleaners, for instance, had to be calibrated so they “moved the residue aside but didn't gouge the soil.” The closing disks had to be tweaked so they grabbed the right amount of soil and built a consistent mound.

A 3-in.-high berm worked well in soybean residue, Kevin says, settling to about 1 in. by spring. But that wasn't high enough in corn residue “because of all the fluffy trash.” The berm needs to be higher on sloping ground, too, he found, to prevent water from flowing down the bare swath.

The short fall window for building the berms and applying fertilizer may be strip-till's biggest challenge for northern growers, Kevin says.

The Lahrs planted corn the last week of April 2009, dropping the seeding rate to 28,000 on sandy knobs and bumping it up to 36,000 in the most productive areas. They applied 4-4.5 gal./acre of 10-34-0 starter fertilizer, “a must and a minimum for 30-in. strip-till,” Werven says. “The dry-banded nutrients get a little too deep to get a true ‘starter effect,’ so we still use liquid starter as a pop up.”

IT WAS COLD when they planted, and the strip-tilled fields “looked kind of ugly,” Kevin says, but “the corn went in really nice in the strips.” Row cleaners on the planter “did a great job” clearing loose residue that had blown over the strips during the winter.

Unfortunately, it didn't rain for several weeks after planting. Kevin estimates that “we saved about an inch of moisture by not doing spring cultivation.” Likewise, the Lahrs' strip-tilled beans “came up nice and even, where our other bean fields didn't.”

The soil conservation benefits of strip-tillage came home to the Lahrs last spring, too. In March, pounding rains washed away a lot of bare soil. Later in the spring, “We had three days of crazy winds when people lost a lot of topsoil. We had cornstalks blowing, but not much soil.”

The Lahrs' previous tillage system consisted of fall disk ripping, followed by separate spring passes with a field cultivator and coil packer. With strip-tillage, the Lahrs eliminated two spring operations. “All we had to do was put corn in the planter and go,” Larry Lahr says.

In addition to labor savings, strip-till cut the Lahrs' diesel fuel consumption by at least a third, Larry estimates. They also saved $6.50/acre on custom urea application. And banding phosphorus and potassium allowed them to drop the rates by one-third without sacrificing yield.

Still, there may not be a clear savings with strip-tillage, says Greg Endres, a North Dakota State University (NDSU) Extension Service area agronomist. For one thing, strip-till equipment is expensive. The Lahrs invested about $120,000 in their new system and kept their old tillage equipment. On weedy fields, Werven says, “a spring burndown application may be needed in place of your spring tillage pass,” offsetting some of the savings.

A 2008 analysis of machinery costs by NDSU Extension Farm Management Specialist Dwight Aakre estimates that switching to strip-tillage would add $17-20/acre in machinery, chemical and application costs, while saving about $8/acre in chisel plow and field cultivation expense. The comparison didn't include changes in fertilizer expense.

Beyond that, Endres adds, it's hard to put a dollar value on long-term soil productivity benefits.

INTEREST IN STRIP-TILLAGE RISING

Northern growers are becoming more interested in strip-tillage, especially for corn, says Greg Endres, a crops specialist at North Dakota State University's Carrington Research Extension Center. There's also a lot of buzz about strip-till for dry edible beans and sugar beet production, he adds.

Strip-tillage has advantages over both conventional tillage and no tillage, Endres says. “I see strip-till as a nice compromise.” Compared to conventional tillage, it reduces erosion, conserves moisture and preserves soil structure and organic matter. Soil in the bare strips warms up faster than with no-till, he says. Banding fertilizer is more efficient than broadcasting. And eliminating field passes saves fuel and labor.

“Growers are essentially doing their tillage, applying their fertilizer and preparing their seedbed for planting all in one pass,” says Minnesota crop consultant Brent Werven.

Northern farmers worry that reducing tillage will lower yields because of cold, wet spring soils and a short growing season, says Jodi DeJong-Hughes, a University of Minnesota Extension tillage expert. But Upper Midwest research has consistently shown that corn and soybeans grown in a strip-till system yield as well as crops grown with conventional till-age, she says.