The AGCO Crop Care Team designed this year's AGCO Application Crop Tour to show several best practices to maximize the effectiveness of a weed-control program.
'When it comes to controlling weeds, there's this battle going on between productivity, efficacy and drift control,' says
Proper sprayer set-up is key to achieving desired weed-control results.
Using demonstration plots of LibertyLink crops - cotton in
Application timing is crucial for weed-control efficacy
'The problem with waiting for a full flush of weeds before spraying is that some weeds will get way too big and really hard to control,' Lee explains, adding that applicators should read and follow all product label instructions. 'We should control weeds when they're small: four inches or less in height.'
Speed isn't a factor when rate and droplet size are correctly maintained
The AGCO team applied Liberty herbicide at speeds ranging from 5 to 15 mph and with carrier volumes ranging from 10 to 20 gallons per acre. Sprayer nozzles creating droplets of various sizes from medium to extremely coarse also were evaluated.
'From what we saw, as long as we were using the appropriate nozzle to give us the correct droplet size for the speed we were running, we'd get the right coverage,' Goebel says. 'We thought maybe there would be a bigger effect due to speed, but we really didn't see any issues as long as we were doing everything else right.'
Coverage is a key consideration when spraying contact herbicides
With weed-control products such as Liberty, which is a contact herbicide, getting adequate coverage is the most important factor, Goebel says. Achieving proper coverage will vary based on sprayer nozzle type and carrier volume.
At lower carrier volumes, such as 10 gallons per acre, using nozzles that create smaller droplets will help improve control. 'However, smaller droplet sizes increase the risk of drift. Higher carrier volumes provide better coverage but require more tank fill-ups. Applicators need to strike that balance between productivity efficacy and drift,' he adds.
Based on what he observed in the
Sprayers equipped with pulse width modulation systems help ensure applicators are maintaining constant pressure, rate and droplet size no matter the speed at which the application occurs.
Use the correct boom height to increase coverage
Another application factor the AGCO team evaluated was boom height. Goebel says that the coverage penalty for improper height can be severe. The team compared the coverage and weed control achieved with booms at 20 inches and 60 inches above the target.
'Booms often get set too high because applicators don't want them to accidentally hit the ground. But if you're spraying four to five feet from the target, you're not going to get proper coverage, and you'll also likely get more drift,' he says, noting that boom-height control systems take the guesswork out of setting heights. 'Ideally, for 110-degree spray angles, your boom height above the target should equal your nozzle spacing. So, if your nozzles are 20 inches apart, your boom should be approximately 20 inches above the target. At 60 inches, we only achieved about 30% control. The spray simply didn't make it to the target due to a combination of drift and evaporation.'
'If you're trying to get over a lot of acres quickly on a hot, sunny afternoon, boom height is really going to have a big impact,' he concludes. 'These products need to be applied well, and having a good understanding of application equipment setup is the first step in ensuring an effective weed-control program.'
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