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Corn+Soybean Digest


You could almost say that Jerry Zubke has been scared straight. No, not the anti-drug program touted by school systems years ago, but straight and accurate precision farming practices that are beginning to pay respectable dividends.

Zubke, who farms at Milbank, SD, has a toolbox full of precision practices that are all, finally, being combined and used effectively together. They include: global positioning system (GPS), auto-steer, grid soil sampling, Veris soil electrical conductivity and pH testing, variable-rate seeding and fertilizer, and even extensive field compaction testing.

All the tools take more time and patience, especially when it comes to hours spent on the computer. But Zubke says at the end of the year he'll know if he's making money.

“I'm going to capitalize on the potential of my soil,” he says. “I expect to get 15-25% higher yields when it all comes together.”

Zubke is confident he'll save on input costs, such as fewer pesticides, less fuel, less fertilizer and less labor, too. So far, though, he's not sure how much he'll save. “I know I'll save on nitrogen, but I'm not sure about P and K,” he says. “My guess is that we'll pay back all the technology investments in about five years.

“When I'm done combining, I want a profitability map that will tell me which farm and what acres are making me money,” he says.

As a banker turned farmer, Zubke began his technology quest in earnest six years ago when he started strip-tilling. Today, all his corn is in strip-till. He constantly hones his farming practices and integrates all the technology at his disposal.

For example, as a bottom-line farmer, Zubke isn't a big fan of doing anything to his land or crops that isn't absolutely necessary.

“I can deep-till 16-18 in., but I don't want to do that if I don't have a compaction problem,” he says. “My idea is to rip it once and then stay off it. With fuel at $2/gal., all I really want to do is maintain the zone for strip-tilling.”

A die-hard strip-tiller, Zubke has no plans to change, especially when he's getting a 25-50 bu./acre corn yield bump on his heavier ground vs. conventional tillage.

In heavier soils, preparing strips in the fall means less spring fieldwork so he can plant earlier. Although it's been a struggle, he admits his goal is to stay straight, narrow and directly on top of the strip.

Most of Zubke's fields have been soil sampled in 2.5-acre grids. “With strip-tilling, I put fertilizer and seed right in the zone (band),” he says. “I want to make sure the corn finds the fertilizer so more of it's available to the plant. All the nutrients are in the strip.

“I've got the fertilizer directly below the seed for a reason,” he adds. “I didn't put the fertilizer down to use later. It's there to use now.”

Zubke injects phosphorus (P) and potassium (K) about 10 in. deep in the fall and applies nitrogen (N) in the spring. “If I lose N from a fall application, I lose money,” he says. “Besides, it's more environmentally safe to spring apply N.”

He even has Veris soil conductivity maps for nearly 20% of his acres. Soil conductivity tests detect different soil types and textures, and help identify underlying clay pans. “I'm going to add those soil conductivity test results to the equation, too,” says Zubke, who doesn't go anywhere without his Palm Pilot that's chock full of field data. “Eventually, I'll have all the data tied to GPS, especially converting the grid maps to GPS coordinates.”

With all the data he's collected, he's beginning to write prescription maps to vary seeding and fertilizer rates. To complete the data package, the yield information he's gathered since 1996, when he first started using yield monitors, was added.

Zubke also started experimenting with auto-steer technology in 2002 to help him stay on his strips, but was disappointed in accuracy due to satellite drift. “I wanted 1-in. accuracy because I have a 4-in. band with strip-till. If I'm on a sidehill, I can't accept anything less than 1 in.”

This spring, after improvements in GPS technology, he took the plunge and added a John Deere StarFire RTK auto-steer system to his JD 8410 tractor. This fall, he also bought a JD 8520 and JD 9620 tractor and a new 9760 combine, all fitted with RTK auto-steer. Cost for the auto-steer system? About $20,000 per unit, which includes a lifetime subscription to the signal.

RTK systems require a customer-owned GPS base station and radio modem link to provide a correction signal to a roving receiver, yielding accuracy in the plus or minus 1-in. range.

“I wanted the repeatability of RTK so two, three or four years from now I'll always be on the same strips,” he says.

As an extra bonus, Zubke is sold on less operator fatigue since adding the auto-steer component. “I can watch what's going on now because I'm not always trying to stay on the row,” he says. “I know we're at 95% efficiency with auto-steer vs. 70-75% without it.”

Auto-steer technology is catching on 10 times faster than Randy Taylor ever expected it would. “The first time you drive equipment with auto-steer, you'll want to try to figure out how to buy it,” says the Kansas State University agricultural engineer.

“I'm not sure auto-steer saves money, but it takes the drudgery out of an everyday task and provides operator comfort,” he adds. “Imagine driving a car without cruise control. You wouldn't buy a car now without it, would you?

“Auto-steer might not drive any better than you do when you first get in, but after you've been in that seat for 4-5 hours, I'll bet it does,” Taylor says. “Auto-steer is going to drive the same at 8 a.m. as it does at 2 p.m. I don't think you can say that for most operators.”

The only two downsides: retrofitting the new technology to older tractors and the cost — and the cost is coming down every year.

This spring, Zubke bought a new JD 1790 CCS 40-ft. wide planter with 32 row units. “It's got variable-rate seeding controls, but it doesn't have the ability to vary fertilizer rates. I'll vary fertilizer rates in the fall when I make the strips,” he says.

Zubke is sticking with 30-in. rows for corn because of the volume of residue, but is planting soybeans in 15-in. rows. “I was using an air seeder, but I'm getting 5-6 bu./acre better yields with the planter. It's just more accurate,” he says. “I'll plant 30-in. rows with corn and come back next year with 15-in. beans. The next year I'll plant directly on top of the old corn rows.” He'll continue to use the air seeder for wheat.

With the accuracy he now gets from the RTK system, his equipment wheel tracks will all be in exactly the same path every year. “Controlled traffic is finally possible,” he says. “I also use auto-track with the grain cart so I can stay on the same tracks all the time and drive parallel to the combine during unloading. If I do that, I shouldn't have to deep rip any ground at all.”

His son, Tim, is an integral part of making management decisions in the operation, and is particularly adept on the computer.

With the technology available today, he says, “We need to make a profit on every acre. Besides, this is just a lot of fun. I enjoy the challenge and like learning the new technology.”

Compaction Sense

Getting a grip on compaction is another of Jerry Zubke's objectives. In fact, you'll see Tom McGraw astride his ATV running up and down fields, testing compaction areas on Zubke's fields.

“We need to know how deep and where the compaction is,” says McGraw, a field information specialist and owner of Midwest Independent Soil Samplers, who has developed his own computer software that incorporates penetrometer data with GPS coordinates. To get an accurate field map, he makes two penetrometer probes per acre.

McGraw says at 200 psi, compaction begins and affects permeability of the soil. Once a penetrometer reading hits 300-400 psi, root restriction occurs.

“Typically, the biggest compaction offenders on the farm are the grain cart and other heavy-axle equipment,” he says. “With compaction maps we can sometimes avoid driving on those areas that are most compactible. For example, glacial-till soils are more compactible than loess soils.”

Over a 10-year period, McGraw says University of Minnesota-Waseca research shows you can expect an average of a 10-bu./acre loss from compaction in heavy soils. Normally, he adds, 75% of compaction happens on the first pass over the soil. Therefore, controlled traffic is one of the best compaction management tools there is.

“It all comes down to yield,” McGraw says. “Compaction reduces pore space, which reduces water holding capacity and oxygen. And both are critical to crop production. For example, 2-3 days of saturated glacial-till soil can cause a huge reduction in yield. At 7-8 days of saturation, yields can be cut by 80%. The message in this case: If soil is saturated for too long, it's probably time to tile.”

McGraw says controlling compaction all comes down to a three-step approach: Collect field data, make decisions and take action.

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