Photo above: The individual nozzle control system on board this sprayer is capable of turning nozzles on and off to prevent skips and overlaps automatically across the boom width at field speeds well above 12 mph. Photo courtesy of CASE IH
Richard Preston says his Kentucky grain farm represents the “worst-case scenario” for efficiently and responsibly spraying chemicals. His fields are located between creeks and timber and back up to ever-growing residential areas near Elizabethtown, Ky.
“In addition, we’re fighting glyphosate-resistant weeds that have to be controlled in a timely fashion, so sprayer efficiency is a must,” he says. With many non-farmer neighbors, Preston is also concerned with reducing drift from his sprayer to prevent damage to yards and gardens that border his fields.
He grows corn, soybeans, wheat, rye, grain sorghum and canola on irregularly shaped fields, many of which are 15-20 acres in size. Many include grassed waterways that have to be protected from herbicides. About 90% of his operation is no-till.
In southeast Minnesota near Spring Grove, Myron Sylling has more unobstructed fields than Preston, but non-GMO weed control applications on his 1,300 acre corn and soybean seed operation were presenting a yield drag because of overlapped spraying, which resulted in plant stunting.
“We had a fair amount of overlap in turns with our 7-section, 90 foot boom, and the non-GMO chemicals were causing chemical burn and stunting, particularly on soybeans,” Sylling explains.
Both producers made the switch to individual nozzle control (INC) systems early in the 2015 growing season, and both say the new technology solved many of their application problems, saving them considerable money in reduced chemical costs.
INC technology allows increased control over the length of a spray boom from several sections, which might be a resolution of 10 square meters, to individual nozzle control, effectively allowing variable-rate application (VRA) on the basis of an individual nozzle’s spray pattern. In many cases nozzles are mounted as closely as 15 inches apart, which provides for an extremely high VRA resolution in less than 1 square meter. Increasingly, growers are adopting the INC systems because the increased precision allows for reduced chemical use, elimination or reduction of overlap of sprayed areas, and the ability to pass over no-spray areas to protect riparian areas or grassed waterways.
What They Changed
Preston traded his old sprayer with a 60 foot boom for a Case IH 2240 sprayer with a 90 foot boom and Case IH’s AIM Command Pro system. The “Pro” uses pulse-width modulation (PWM) to control individual nozzles across the span.
How PWM Works
A Pulse Width Modulation (PWM) sprayer system operates at a constant system pressure and delivers product through solenoid-equipped nozzles controlled by an on-board microprocessor, says Kansas State University agricultural engineer Ajay Sharda.
“The system pulses 10 times per second, and within each pulse the nozzle solenoids can be operated at different duty cycles — opening and closing in 100 milliseconds — depending upon the need for a given application rate at the location of the nozzle,” he says.
Sharda says the input to the solenoid from the microprocessor is a square wave that has a duty cycle equal to the ratio of the time the nozzle is on vs. the time it is off. A 100% duty cycle indicates full flow through the nozzle for the full length of 0.10 second pulse and a 0% duty cycle indicates no flow through the pulse. The variations between these two conditions produce the variable amount of fluid passing through the nozzle.
“A nozzle on half of the pulse and off the other half would be said to be in a 1:1 duty cycle — flowing 50% of the time,” he says. “A nozzle flowing through only one-tenth of the pulse would be described as having a 1:9 duty cycle.”
During a turn with a long boom, Sharda says, a nozzle on the outside of a turn might be operating at a 100% duty cycle — on the full one tenth of a second — while in the middle the nozzles are operating at a 1:1 duty cycle. Those on the far side of the boom, on the inside of the turn, might be operating at 2:8 (20%) or 1:9 (10%).
PWM systems use a constant system pressure and a GPS-driven microprocessor to vary the time the nozzles are on or off during 0.10 second pulses to meet the application rate.
“With glyphosate resistance becoming a problem, we’re moving to more residual-type herbicides and any overlaps with those products will damage our crops,” Preston explains. “Also, we wanted the extra precision to control droplet size and the potential for drift, particularly where we farm so close to residential neighborhoods.
“The system is very good for controlling drift and minimizing overlaps, so it’s proving to be very good at helping me protect my neighbors.”
Preston says the more borders one has to farm around — with irregularly shaped fields, stream banks, waterways and strips of timber — the more economic advantage can be gained with individual nozzle control keyed to GIS information.
“As we drive into pointed areas of a field, the system automatically shuts off nozzles in areas that have been previously sprayed, which reduces overspray,” he explains. “The system also allows me to protect my fescue/clover grassed waterways from herbicide damage. After the system is programmed for my fields, it automatically turns off the nozzles that overhang these areas as I drive past them.”
Preston says the increase in boom length from 60 feet to 90 feet gives him significant boosts in efficiency in spraying time in the field, and 2015 results indicate the money saved in chemical costs will make almost one-third of his sprayer payment per year.
Sylling used Pentair/Hypro’s ProStop-E nozzle control valve system to retrofit his sprayer to INC capability. The ProStop-E setup doesn’t use pulsed spray nozzles to vary application rates, but employs a ball valve at the nozzle to provide instantaneous on-off control, depending upon cues from the controlling microprocessor. The Hypro system, which uses variable system flow rates, can operate on digital ISO signals or analog 12-volt control systems.
“Our retrofit gave us 24 sections of control across our 90 foot boom and that significantly reduced overlap sprays that wasted chemicals and caused yield loss from temporary plant injury,” Sylling says. “We ran tests on one 600 acre terraced soybean field and the increased precision saved us 16 acres of chemical just in reduced overlaps, compared with our previous system.”
Sylling also estimates eliminating the overlaps on those 16 acres would amount to a 3-4 bushel yield increase on the affected areas by not over-dosing GMO soybean rows with glyphosate.
Precision Boosts Productivity
John Lang, application engineer for Pentair/Hypro, says regardless of the brand or engineering design of an INC system, the technology adds automation and precision to spraying. “Using GPS technology for tracking purposes, INC uses computer-driven valves to control the flow of crop protectants,” he explains.
“Once an operator ‘maps’ a field — creating an outline of the area to be sprayed and areas such as washes, waterways, wetlands and other hazards that aren’t sprayed — the computer controls the flow of each spray nozzle as it passes over the field,” he says. “The system will interrupt the chemical flow to those nozzles that are in recognized areas not intended to have chemicals applied, and it will terminate the flow of nozzles that are in an overlap area that has previously been sprayed.”
Chemical savings from reduced overlaps can be significant says Tony Stueve, western region field marketing manager for Capstan Ag Systems. Capstan’s PinPoint INC system is a PWM design used in a variety of OEM sprayer systems, including Case IH’s AIM Command PRO.
We ran tests on one 600 acre terraced soybean field and the increased precision saved us 16 acres of chemical just in reduced overlaps, compared with our previous system
“With conventional sprayers with auto-boom shutoffs, most applicators mix up to 10% more product than what the field requires,” he explains. “Because of the increased precision of INC systems, I have customers who now mix 1,010 gallons compared with the 1,200 gallons they mixed with conventional systems. That’s a sizeable savings in product and water.”
Stueve says operators using INC on large, flat, square or rectangular fields regularly claim an 8% saving in chemical costs, while growers on smaller, irregular-shaped fields with many obstacles report savings around 20-22%.
Cashing in on Turns
In western Nebraska, where the University of Nebraska operates a demonstration INC system, crop specialist Robert Klein says one of the more significant advantages INC technology has over conventional sprayers is automatic turn compensation in the application of chemicals.
“When a spray boom is operated in a turn, the nozzles on the outside of the turn pass over the crop much faster than those on the inside of the turn,” he explains. “Traditionally, this has caused significant under-application on the outside, and just as significant over-application on the inside of turn.”
Kentucky research shows application errors as high as 25% are common due to velocity variations across a sprayer boom in a turn — causing significant efficacy issues with pesticides and with weed control in the case of herbicides. “This uneven application adds to weed resistance in under-applied areas and potential crop damage where the chemical has been over-applied,” Klein adds.
“Another benefit of INC systems operating in turns and uneven terrain is the instant on-and-off action of individual nozzles,” Klein says. “With a conventional sprayer with boom-section control, it takes 2-8 seconds to drop pressure in the system to the 7-12 psi levels necessary to close a nozzle.
“Similarly, it takes even longer to build that pressure back to operating levels once it has dropped. At 10 mph, the sprayer is traveling 14.67 feet every second. So in 5 seconds, the sprayer has moved more than 73 feet. Today’s INC systems eliminate this lag time.”
Outlook for ROI
Individual return-on-investment varies by farm and field, says Nick Langerock, product manager for Raven Industries, maker of the Hawkeye PWM system. “The more terraces, waterways and no-spray zones you have, the more the individual nozzles will be shut off and that’s what builds ROI,” he says.
“We’ve run different comparisons on a popular profit calculator spreadsheet and figure if you’re farming 3,500-5,000 acres, you could expect a payback for a typical $18,000-$30,000 INC system in 1-1.5 years.”
Similarly, Auburn University research shows conventional sprayer technology operates at about a 10 meter resolution, whereas the most precise INC systems can achieve resolution under 1 meter.
In field-size no-till plots, that improvement showed a 15% minimum reduction in the total quantity of glyphosate applied. The authors concluded the reduction in chemical use alone would easily justify the expense for the technology for intermediate to large U.S. grain farms.
Special Report Table of Contents
Three years of low grain prices are forcing farmers to minimize production costs. Developments in how they apply inputs will be an important part of growers’ cost cutting.
Few signs point to a recovery in crop prices in the near term, which is making it imperative growers find ways to hold down costs.
Developments in applying crop nutrients and pesticides have come fast and furious during the last decade. Many of the newest breakthroughs are aimed at ‘site-specific’ management of inputs, nozzles and individual nozzle control, and soil applications.