Field Notes: Observations About RTK Auto-Guidance

October 6, 2009 07:00 PM

By Bob Stewart

We have been using an RTK GPS auto-steering system since 2004. An Ag Leader Insight monitor controls the Trimble auto-steering system, as well as rate control, rate logging and the yield monitor in our combine and stores our A-B lines for each field.

Perhaps some of our observations about RTK auto-guidance will be of interest if you're considering purchasing a system.

We use auto-steering for tillage, planting,  anhydrous ammonia application, spraying, sidedressing nitrogen and harvesting.

One benefit of auto-steering is that it moves us toward controlled traffic. Our tractors, combine and grain carts are all on tracks on 120" centers. The wheelbase of our high-clearance sprayer is also 120". Running in the same tracks as much as possible reduces soil compaction.
Mixing equipment sizes. With 24-row (60') planters and a field cultivator (actually it's 62' but it runs on a 60' pass), 60' sidedress applicators, a 90' sprayer and a 40' combine head, we can't always run in the same tracks, but we never run over a row. With RTK-based GPS we rarely can find the split between the 24-row planter passes, which allows us to come back in and harvest with a 16-row head.

We still run diagonally when we do fall tillage because we haven't found a fall tillage tool that adequately takes out the old corn rows. We are not as concerned with wheel traffic patterns in the fall since we do fall tillage.

When field cultivating in the spring, we go with the rows. Then, the planter tractor follows in the same tracks as the cultivator tractor. It's hard to put a dollar value on controlled traffic, but we know that when we used to work fields diagonally we could see the wheel tracks in the young corn.

In 2006, RTK auto-guidance helped pay for itself harvesting downed corn. We had 200 acres that were nearly flat and you could not find the rows. Auto-steering probably saved us close to 20 bu. per acre, and it let us harvest faster since we could keep the machine right on the row.

Other benefits we've observed include reduced operator fatigue, which lets us run longer hours. The field maps that display on the monitors show the operator's location, which helps him determine if he's in the right place. We record field boundaries and A-B lines ahead of planting, so there's no guesswork about how to plant the field. Since we don't have markers on our planters, we set A-B lines for headlands, as well as for the planting across the field.

We've noticed you get a little more wandering when using auto-steering with wheeled vehicles than with tracks. And with the height and high speed of our Hagie sprayer—12 mph or more—we get a little movement. We still use auto-steering, but we have to pay attention and occasionally nudge the sprayer back onto the row.  

With complex equipment like this, there will occasionally be some downtime. But it hasn't been bad—I don't think we've averaged a half day lost per season due to equipment failures.

We carry a laptop computer in the field to download updates and new software. If we're a long way from our dealer, he can usually assist us over the phone to troubleshoot a specific problem with the auto-steering system. 

Losing the RTK signal can be a problem. Where we farm in central Illinois, the signal reaches out 7 miles from the tower. But around our farm in northern Illinois, the ground rolls more and there are tree lines. We solved the problem by putting a repeater in a pickup to bounce the RTK signal around obstacles.

I recommend investing in a repeater if you are going to run equipment on RTK. A repeater can help you get an RTK signal in pockets that would otherwise not have a strong signal.  

We get our signal from a network in central Illinois and from our own base station in northern Illinois. I suggest using an RTK network if possible because maintaining your own base station can be a problem. 

Anticipate a learning curve for your employees. It's not bad—after a couple hours of experience, a person can do tillage; a little more experience is required for planting. 

Before buying a system, make sure the dealer has good support—24-hour support if you plan to run all night.

For us, RTK auto-guidance was a sound investment. This spring, we will pair it with automated planter unit controls to cut overlap and save seed.


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