As Larry Diedrich finishes scanning the newspaper, he reaches for a magazine to read, casually glancing back through the tractor cab — mostly out of habit — to check the planter. These days, with his new auto-steer setup, he can practically plant corn in the middle of the night with his eyes closed.

Precision auto-steer technology, married with labor-saving strip-tilling, has made planting nearly stress free for this Elkton, SD, farmer. Better still, it's paying for itself.

Larry and his brother David are veteran strip-tillers, with eight years experience under their belts. Last season, for the first time, they added auto-steer to their 4,500-acre operation.

“It's amazing technology,” says Diedrich of his Trimble global positioning system (GPS) teamed with auto-steer. “We're never off center more than a half inch with the AgGPS Autopilot System. And the system even compensates for global drift with RTK, or real-time kinematic. Without that, you could be off 30 in. in a 24-hour period.”

Auto-steer units operate with GPS that's plumbed into the steering mechanism of a tractor. After the first pass through a field, an on-board computer calculates where each pass needs to be to match up perfectly with implement width.

At the end of a row, after turnaround, the computer locks onto the next path and the auto-steer takes over the tractor's steering, moving Diedrich over exactly 40 ft. when planting. However, anytime he turns the steering wheel, it overrides the auto-steer system and manual steering takes over.

“I'm pretty high on auto-steer and think it deserves a good, hard look,” says Mark Hanna, Iowa State University ag engineer. “But, you need to carefully evaluate the technology and when it will make sense for you. If you're moving to new equipment, this might be the right time to add it.”

The Diedrichs' $45,000 Trimble system has a stationary satellite GPS signal unit atop a 130-ft. grain leg located on the farm. That unit transmits signals about 10 miles in a line-of-sight for the auto-steer tractor. To receive and strengthen that signal in the tractor, they then use a repeater unit that's mounted on a 10-ft.-tall pole they've rigged to the back of their pickup. The repeater can be positioned up to five miles from the tractor and still transmit a saturated signal as long as there isn't a tree or hill obstructing the line.

“When we planted last spring we occasionally lost a signal, but we wondered if that wasn't a by-product of military controls during the Iraq war,” Diedrich says. “Still, the equipment is new and we expect there will be a few disruptions.

“With this system it's easy to plant through the night,” he adds. “I don't spend time looking forward. I just turn and look backward to make sure the planter is operating correctly. I can plant about 30% more with this setup than before.”

The big advantage to the system, Diedrich claims, is that he can plant over his strips more accurately. “When I used to get off the strip, I saw a noticeable difference in yield.”

That extra yield is in addition to the whopping 15-bu./acre yield bump they got when they first moved to strip-till from no-till.

“I expect a big increase in auto-steer technology in the next few years, especially where you're strip-tilling or have compaction concerns,” says Tony Vyn, Purdue University cropping systems specialist. “Besides faster field speeds, it's accurate for precision planting and fertilizing. It also saves costs because of less fertilizer use and herbicide overlap.”

Purdue research shows about a 20% increase in field speed with auto-steer. In addition, farmers are able to work longer hours with reduced driver fatigue.

“It's harder and harder to find people to operate farm equipment,” says Purdue ag economist Jess Lowenberg-DeBoer. “But now, with auto-steer, the operator's skill is less of an issue.”

Auto-steer is catching on in other countries, too. In Australia, for example, controlled traffic — which translates into controlled compaction — is an important reason why auto-steer has been embraced.

“By following the same tracks in fields, they've been able to almost double their wheat and canola yields in some places,” Lowenberg-DeBoer says. “These highway-like tracks are compacted and dry out quickly so you can get into fields earlier after a rain. And auto-steer helps keep them on the row when they're doing mechanical weed control on large acreages.”

The Diedrichs use a DMI 16-knife strip-till machine to build their strips in the fall. “When we decided to go to auto-steer, we wanted a tractor to handle both the strip-till machine and our new 16-row (30 in.), 40-ft. John Deere 1770 NT CCS planter,” he says. For less compaction and better traction, they decided on a Caterpillar LT 765 track tractor.

Total investment in new equipment to maximize efficiency for the switch to auto-steer ran $265,000: a Trimble system at $45,000, a Cat tractor at $145,000 and a new planter at $75,000. They already owned the strip-till machine.

With this system Diedrich says he can plant about 400 acres/day, or about 20 acres/hour, including fill times. Planting speed averages 5º mph.

He expects the auto-steer investment to pay for itself in just two years. The big return, he claims, comes in their ability to plant more corn acres because they can now handle the acres with the new auto-steer system. Currently, they plant 3,600 acres of corn and about 750 acres of soybeans. However, the brothers plan to move toward continuous corn, which means more pocketable profit.

“By planting directly over the strips, we think we can easily make $75-100 more an acre with corn on corn compared to a conventional corn-soybean rotation,” Diedrich says.

When building their strips in the fall, they split 30-in. rows down the middle and plant every 15 in. “In two years we'll be planting exactly over the original row area that's been fertilized before and hope to see some yield advantages with that, too,” Diedrich explains.

A big plus with the system, he adds, is that if they have to avoid a wet area when planting, they can come back later and accurately finish the job. “If we need to skip a wet spot, for example, we mark down the round, say 48-54. Then, when it dries out, we go back and plant in the exact same rows. In conventional tillage, it's easy to see the rows. But that's not so easy in a limited-till situation.”

Diedrich believes the whole auto-steer phenomenon will be more popular once satellite drift is under control and the signal can transmit more than 10 miles. “Too many big farmers have land spread out over several miles and it's not practical. That will change as the technology changes.

“Still, on a scale of one to 10, I give this system a score of mostly a nine or 10. Some days, though, when the signal isn't strong, it only gets a two,” he says.

Precision Basics

Depending on the level of accuracy required, there are two primary levels of GPS precision available, according to Daniel Humburg, South Dakota State University ag engineer.

  1. Differential GPS (DGPS) systems offer accuracy from 4 in. to several meters. These systems commonly rely on one of three sources of differential correction data to improve the basic GPS position fix.

    • The Coast Guard beacon, which is a free signal and generally provides accuracy in the 1-3 meter range, depending upon the GPS receiver used.

    • The Wide Area Augmentation System (WAAS), which is a free signal broadcast from a government satellite. Its accuracy is similar to the Coast Guard Beacon data, but it's available everywhere in North America.

    • Commercial differential services, which are offered through private companies, including equipment manufacturers. These services are also broadcast from satellites and marketed at different costs and levels of potential accuracy. Some offer accuracy as fine as plus or minus 4 in. of error.

  2. The more precise Real-Time Kinematic (RTK) systems use a different approach to estimating receiver-to-satellite ranges called carrier phase positioning. These systems require a customer-owned GPS base station and radio modem link to provide a correction signal to a roving receiver yielding accuracy normally in the plus or minus 1-in. range.

For more information about auto-steer technology, check this Virginia Tech Web site: http://www.ext.vt.edu/pubs/bse/442-503/442-503.pdf. And ask your local equipment dealers — many already offer the technology.

Strip-Till Growth Spurt

Strip-till is growing across the Midwest, says Tony Vyn, Purdue University cropping systems specialist. In Indiana, he projects about a 25% growth rate from 2003 to 2004.

In Illinois, about 25% of no-till corn acres are now in strip-till, says Dan Towery, natural resources specialist with the Conservation Technology Information Center. “Manufacturers of strip-till equipment are selling out,” he says. “Auto-steer and strip-till are a perfect fit.”

Strip-till combines the soil drying and warming benefits of conventional tillage with the soil-protecting advantages of no-till. Vyn says corn grown in a strip-till system consistently yields as well as corn grown in a conventional-till system. It can also yield better than no-till corn planted on the same date.

In high-residue areas, strip-till forms raised, narrow strips, or berms, about 3-4 in. high and 10-12 in. wide. Normally, strips are for crops in 30-in. rows. Soil on either side of the berms remains untouched. Strips are made in the fall, following harvest. By spring, the berms have settled to about 1-2 in. and seed is planted directly into the strip rows.

The big advantage of strip-till, Vyn says, is the additional planting flexibility on soils with poor or variable drainage.