Do you know how much fuel you use on your farm each year? And do you know where you use most of it?
The answer might surprise you, Iowa State agricultural engineer Mark Hanna told growers at the university’s annual Integrated Crop Management conference in Ames on Dec. 3.
“It’s a pretty reasonable bet that there are a lot of folks out there using 4 to 6 gallons of diesel per acre on row-crop operations,” Hanna said of Iowa growers. Planting, spraying and harvesting take up their share of fuel, but more than half of that amount is likely burned up by tillage, he added.
With commodity prices low and diesel fuel hanging stubbornly around $3.50, it could be well worth your time to scrutinize every planned tillage pass, Hanna pointed out.
Recent studies have shown that tweaking factors such as the number of tillage passes, the depth of the tillage, the speed of the engine, and even the use of the four-wheel-drive option can save growers thousands of dollars across large acreages.
TRIMMING TILLAGE PASSES AND DEPTHS
Data from Iowa State’s six research farms suggest there is a direct relationship between the depth of a tillage implement and the amount of fuel a tractor uses, Hanna explained.
One trial showed when a field cultivator was raised from a 5-inch depth to a 3-inch depth, the tractor used 8% to 10% less fuel.
“On deeper tillage operations, the savings are even more dramatic,” Hanna added.
A University of Wisconsin study evaluated a subsoiler tillage implement running at four different depths ranging from 9 to 18 inches deep. At 9 inches, the tractor used 1.75 gallons of diesel per acre; at 18 inches, it burned through 3 gallons per acre.
Perhaps most importantly, the Wisconsin researchers saw no difference in the corn yields between the four different tillage depths in the trial, Hanna pointed out.
Likewise, soybean yields over the past five years on Iowa State’s research farms show no discernible difference between the broad range of tillage operations practiced, he said.
“You need to stop and ask, how much is this tillage adding to my profitability here? Is it increasing my yield enough to pay for it?” Hanna said. In the absence of compaction problems, it has been difficult to document consistent differences in yield between tillage techniques, Hanna added later in the talk.
Based on their studies of fuel use in tillage, Hanna estimated eliminating one primary tillage pass or two secondary tillage passes could translate to $5,300 dollars in fuel savings on a 1,000-acre field (when diesel was estimated at $3.50 per gallon).
Even if farmers cut out only one secondary tillage pass, or just raised their tillage depth a little bit, Hanna estimated they could save about $2,600 across a 1,000-acre field.
SHIFT UP, THROTTLE BACK
Engine speed plays a surprisingly significant role in unnecessary fuel use, Hanna said.
“On lighter loads, shift up, throttle back,” he suggested. “Take advantage of running at a lower engine speed in a higher transmission gear, and you’re going to do the same operation out there but burn less fuel.”
In one telling Iowa State study, researchers ran a field cultivator across a field at 5 mph, in gear C1, at just under 2,100 revolutions per minute (RPM). When they shifted up to gear C2 and throttled back to 1,700 RPM, fuel use dropped by 22%.
Across 1,000 acres, Hanna estimated this drop in fuel use translated to 300 gallons of saved diesel, worth more than $1,000.
On a strip-tillage operation in another trial, researchers saw up to 33% fuel savings when they shifted up to C2 and ran at 1,710 RPM instead of running in C1 gear at 2,170 RPM, Hanna added. He estimated those savings equaled 710 gallons of saved diesel on a 1,000-acre field, or nearly $2,500.
“My guess is that some of the hired help or other family members — not you! — are consistently running that tractor at 2,100 to 2,200 RPM all the time because they want to make sure they’ve got plenty of reserve power,” he told the conference attendees. “But you’re wasting quite a bit fuel that way.”
Another quick fuel-saving trick is to engage your front-wheel drive when you are in the field, Hanna added.
In one trial, the researcher ran the tractor in multiple scenarios — drilling cover crops, moving large bales, hauling corn — with his front-wheel-drive option alternately engaged and disengaged. To his surprise, the tractor showed an impressive fuel savings of 7% to 8% when the front-wheel drive was engaged.
While it’s probably best to disengage the front-wheel drive on the road between fields, it appears to be worth switching the option on for field operations, Hanna concluded.