THE latest generation of weed detection technology is set to reduce herbicide costs considerably, according to Weedseeker.

The technology is also claimed to help minimise glyphosate resistance.

With NSW DPI research indicating weed cover in fallow paddocks is as low as 20 per cent, up to 80 per cent of herbicide is applied to bare soil.

WeedSeeker works via sophisticated electronic circuits that analyse reflected light and determine when it matches the light reflected by green plants. When a weed is identified, it triggers a solenoid that sprays the plant.

Russell and Sharon Hocking crop 3000ha at Milloo, just west of Rochester, and introduced a WeedSeeker in 2010.

The Hockings bought a second-hand 24m GoldAcres Ground Glider and Southern Precision fitted the WeedSeeker system on to the boom, with an 800 litre tank and its own spray pump.

At the same time, they bought a new GoldAcres trailer with a 6500 litre chemical tank and three direct chemical injection units.

The boom is fitted with twin spray lines and 64 solenoid/nozzle units.

The twin spray line set-up is run simultaneously - the larger tank doing a blanket spray of light chemical for the small weeds and the Weedseeker targeting the larger weeds.

This year, the Hockings have mainly used Roundup, Surpass and Garlon through the 800 litre tank and topped it up via the large tank.

"Saving money on chemical was the main issue behind purchasing the WeedSeeker system," Russell said. "Two years ago we were spending $90,000 a year on chemical. It was a simple sum to do.

"At the first spray, you'd save about 10 to 15 per cent of the chemical. It's with the second and third sprays that you get the big savings."

He said the unit may need to be re-calibrated for each paddock.

"You park it on a patch with no weeds, hit the calibrate switch and it sets the standard that it will operate to. On some paddocks, you need to use the sensitivity switch. You calibrate for the lighter soils and the darker soils are more sensitive."

Last summer, spraying 300ha, the savings in chemical in the different paddocks varied from very little to 50 per cent.

"The farm ends up very clean. For example, we get Bathurst burrs here that are usually not enough to spray for, but too much to cut. We just go and spray them with the Weedseeker.

Plus we have a marshmallow problem that is usually very expensive to fix.

"It really is more efficient in more ways than one - we can go all day on one tank of chemical and reduce refilling time, labour and fuel."

Weed detection technology also helps reduce off-target drift.

Steve Lanyon, at Boort, north of Bendigo, is an early adopter of the system, having fitted a Weedseeker in 2008 after seeing it at the Speed Field Days.

Farming 4000ha with his father Trevor, Steve built a 20m trailed boom set up with a 5000 litre main tank to suit their controlled traffic system. The 52 sensor units have 38cm spacings.

They use two boom spray lines, one for a blanket spray, the other for the Weedseeker.

"At that time Roundup was $15 litre and we were spending $84,000 on summer spray. The Weedseeker is used mainly in summer, very rarely at other times. It works on all varieties of weeds and is excellent on melons and Bathurst burr," Steve said.

In the first year they saved $48,000 on Trevor's farm.