THE late arrival of his WEEDit boomsprayer this year has provided Bonnie Rock farmer Nick Priest with some food for thought.
“We got it in March and with the start to the season it went straight into the paddocks,” Nick said.
“It didn’t require any calibration and the pressure was on because we had a 10,000ha cropping program ready to go.
“We sprayed with the WEEDit using between three and four litres (a hectare) of Roundup and what surprised us was the amount of chemical left in the tank.
“We sprayed three to four days in front of the seeder, including night work where you can see the red laser lights cross the boom and pick up the chemical “puffs” activated by the WEEDit sensors.
“In one 450ha paddock we only sprayed the equivalent of 30ha.
“It was deceiving looking at paddocks where you would normally think you should only blanket spray.
“In that particular paddock it cost us $500 in chemicals where normally a blanket would have cost $4000 and based on our overall cost savings of about 80 per cent, we’ll pay for the machine in two seasons.”
Needless to say Nick is very happy with the WEEDit – he opted for a 5000 litre tank and 36 metre (120ft) boom.
“It’s easy to use and you don’t need big power while spraying at between 16 and 22km/h, depending on conditions,” he said.
“Based on our experiences this just won’t be a spot-sprayer for summer programs.
“We can use it year-round, particularly to spot-spray chemical fallow paddocks and keep pressure on weeds.”
The technology used to operate WEEDit spot spraying involves a system of linked sensors which scan the soil, emitting red light to detect unwanted plant life.
In operation, one sensor covers a one metre section within which space are five individual nozzles.
The sensors sweep the ground at a rate of 40,000 times per second.
The natural plant chemical chlorophyll responds to the red light by absorbing it and emitting near infrared (NIR) light back onto the sensors.
The WEEDit sensors pick up even the tiniest specks of NIR, and react by activating particular sets of spray nozzles.
Each individual spray solenoid opens up in one millisecond, blasting the targeted weed with a lightning-fast precision bombardment of chemicals.
The latest WEEDIT models use LED lights which are 150 per cent brighter than older models and are equipped with pulse width modulation (PWM) to control the rate of chemical that is applied by each nozzle spaced at 20cm (8in) along the entire boom width.
Operators have the ability to apply a light blanket spray across the entire paddock but also ramp up chemical to full-rate where a plant is detected.
Nick’s only problem was a flock of 28s (ring-necked parrots) chewing the wiring to the sensors during a period when the WEEDit was shedded.
“I saw them flying out of the machinery shed so I knew where to look for problems,” Nick quipped.