WEEDS are estimated to cost Australian agriculture in excess of $1.5 billion a year, while improving spray efficacy is essential for farm profitability, it is also imperative farmers reduce drift in an effort to retain the social licence required to apply chemical.
Pending changes to the application rules for foundation herbicide 2,4-D by the Australian Pesticide and Veterinary Management Authority (APVMA), raises questions about the suitability of spray technology and nozzle combinations sold in Australia.
Pulse width modulation (PWM) spray technology has become increasingly popular amongst sprayer manufacturers in recent years.
Case IH, Australia New Zealand, product manager Andrew Kissel said the companies PWM system, known as Aim Command, had been in production for about 15 years.
“Aim Command holds your pressure constant while it varies the duty cycle on the nozzles to match the application rate required,” he said.
“We use a ten hertz pulse frequency, which means they pulse ten times a second.
“All we do is vary the amount of on versus off time in those pulses and that we refer to as duty cycle.”
While the technology potentially allows consistent droplet size independent of the speed the spray rig is travelling, nozzle selection could be considered a drawback of the technology.
“We don’t run air-induction tips is because they rely on a constant stream of product coming through to draw a venturi to get the air to come in,” Mr Kissel said.
“If you put it on any of our systems, it actually will spit water back out of those air induction ports, so we strongly advise not to.
However Mr Kissel said operators using the Aim Control Flex technology could switch the spray mode, turning off pulse width modulation and returning to static spraying to allow the use of air induction nozzles.
“Typically we have six different modes you can spray in, but most customers will use two or three of them,” he said.
“Our standard mode with pulse width modulation, a blended pulse mode and the off mode for fertiliser or air induction nozzles, some of those things that are a little less sensitive to holding the pressure constant.”
Though the current Grains Research Development Corporation (GRDC) nozzle selection guide shows very few, if any, nozzles suitable for applying very course droplets across a range of pressures, Mr Kissel said Wilger nozzles were capable of the spectrum while maintaining coverage.
“With the Wilger nozzles we use a DR drift reduction nozzle, that gets us in the right spectrum,” he said.
“The nice thing about this system versus an air induction is, with an air induction you have the bubble you are relying on first,” he said.
“With this I can pick the right tip and put a higher pressure so those droplets have more force to get into the crop canopy and break and stick to the leaves in there.
“If you are trying to shoot for that extra course droplet, around 500 microns, you can use a tip, pressure and rate to do that, consistently across the field.
“So we pulse all our systems on the Aim Command, Aim Command Pro or Aim Control Flex.”