The high-clearance sprayer is a workhorse of the contemporary farm. These machines hit the mainstream about 20 years ago with foldout, rear-mounted booms, and many farmers rely on the technology to apply crop protection agents faster and more accurately.
Some manufacturers offer a frontmounted boom, and that has many scratching their heads. What’s up with the shift in boom placement? Is there some kind of advantage to that placement? What should farmers know before they buy?
Tom Wolf of Agrimetrix understands why farmers are curious about the frontmounted sprayers. “Farmers are the most science-literate occupational group that I know,” he says. “Science has given them a tremendous return on their investment and when they see a change like this, they say: ‘Hey, what does the data say?'”
Agrimetrix specializes in agricultural spray research, but even Wolf admits that information comparing the spray deposition of rear- versus front-mounted booms is sparse. He’s hopeful future research will clarify the data. “For now, it’s best to think of it as simply an alternative way of mounting the boom and to consider what works best for your farm,” says the former Ag Canada researcher.
On the ground, though, farmers who have made the switch like the view, says Dennis Gerbrandt, a sales manager with Robertson Implements in Swift Current, SK. “You see all your nozzles and if you’re going around an obstruction in the field, be it a power pole or a rock pile, it’s all right there in front of you.”
New Holland’s machine, with the boom out front, water tank in the middle and the engine mounted at the rear, is well-balanced from front to back. Some operators believe that causes fewer issues with soil compaction, says Gerbrandt.
He and Wolf agree that farmers who are thinking about making a switch can weigh a few pros and cons. Below, they outline a few key issues to think about:
Equipment handling and spray accuracy are issues every time a spray boom navigates a turn or corner, says Wolf. The outer edge of all booms travels faster than the inner edge, which compromises spray deposition from booms without turn compensation. It’s why some farmers will drive straight into a corner, then back out, turn into the corner the other way, and go straight out from there.
He says the front-mounted boom doesn’t really offer an advantage here. “Yes, you can drive into the corner and stop, back out, turn and start the new pass where the spray boom ended,” says Wolf. “But with the rear-mount sprayer you would simply do the opposite. There’s no clear winner.”
Front-mounted units offer improved visibility as the operator can see most nozzles. “On the rear-mounted boom there’s always a section of the boom you simply can’t see,” says Wolf. “The middle third is always obscured and you’re reduced to hoping that everything’s okay back there.”
Auto-steer helps by allowing operators to keep a better eye on the rear-mounted boom because they can spray without a hand on the wheel. “Nonetheless, there is an advantage to seeing everything in front,” says Wolf.
The ergonomics of facing forward are also better for the operator, says Gerbrandt, “Let’s face it. You might spend 10 hours spraying. Being able to focus forward is a lot easier on the body. Drive your car for half a mile down the road forward and then back up for half a mile. You’ll feel the difference.”
Cameras connected to a dash-mounted screen can be used to monitor rearmounted booms and spray nozzles from the tractor cab, notes Wolf. This solves visibility and ergonomic issues.
Farmers often ask Wolf about spray drifting back onto the tractor and operator of front-mounted units. With a frontmounted boom their concern is driving straight through a spray cloud, which can make the ladder that they climb down wet.
There is a simple solution: frontmounted boom operators can avoid stepping onto freshly sprayed land by shutting off the boom and driving a bit further before they exit the tractor. This allows them to descend onto unsprayed land from a ladder mounted at the rear of the machine. “Most of the time, the spray cloud stays pretty low, and that ladder will remain dry,” adds Wolf.
Spray drift can be an issue with a rearmounted unit, too, says Gerbrandt. The bottom line is that operators must manage the issue, regardless of boom placement.
Tractor unit turbulence and its affect on spray cloud displacement is an issue for both rear- and front-mount units. It affects the smaller drops more than the bigger ones because smaller drops remain airborne for longer.
“We have some data that shows that the wheels and other elements of the sprayer redistribute the spray somewhat,” says Wolf, referring to rear-mount units. “That can result in regions under the boom that are underdosed, or overdosed. That lack of uniformity is inefficient.”
Wolf hasn’t yet compared front- and rear-mounted booms for this issue. “We suspect the turbulence problem won’t be entirely solved by having a front mount.”
Front-mounted booms were launched decades ago with Hagie (recently partnering with John Deere) and Miller (now also making sprayers for New Holland) hitting the market first.
Those early units were designed for row-crop production, since the frontfacing view helped operators accurately place products such as liquid nitrogen fertilizer between rows of corn. For most non-row crops, that advantage is less important.
Best practices still rule
The unvarnished truth about crop protection products applied with giant machines is that timing is critical and uniform application can be tricky.
“If you have regions where you overdose, you are wasting the material,” says Wolf. “If you have regions you underdose, you have possible loss of disease or pest control.” Since mistakes aren’t usually noticeable for a week or two after spraying, efficient use of these machines and products all comes back to preventing coverage problems through best practices.
“The traditional best practices that we’ve been promoting have been to drive slower, to lower the boom and to use coarser sprays, all of which contribute to uniformity,” says Wolf. “And we do have supporting data that shows these practices help provide a more uniform deposit. These are the things we should be doing.” And doing regardless of boom placement.