Spraying herbicides between rows to hit the weeds and not the crop could give producers more bang for their weed-control buck, but more research is needed, says Agriculture Canada research scientist Tom Wolf.
Inter-row spraying has caught on in Australia, where farmers use hooded sprayers to apply non-select herbicide between rows.
Wolf, an expert in sprayer technology and nozzles, is now looking at this technique in North American cropping systems and outlined his research at the recent Advanced Agronomy conference in Leduc. Little research has been done on low-drift nozzles, said Wolf, although he has been working with them since 1997. He initially tested the nozzles with colleague Eric Johnson, a fellow researcher and found they did reduce drift and expand opportunities in precision spraying.
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“Timely removal is everything in weed control and it’s even more important in disease control,” said Wolf. “A good spray applied at the wrong time doesn’t really do its job at all.”
The Agriculture Canada lab has a laser that enables researchers to track the flow of a spray. Wolf and his team members tracked the size and drift of spray droplets from both a conventional nozzle with 40 psi and a low-drift nozzle with 40 psi. They found the low-drift nozzle produced fewer droplets in a size fraction that corresponded with lower amounts of drift.
“We’re not eliminating driftables, we’re just reducing the proportion of them,” said Wolf.
Minimizing drift is important for all herbicide applications, however inter-row spraying will require even greater precision or physical separation of herbicide and crop.
Expanded in-crop options
Inter-row spraying could expand in-crop options for specialty or low-acre crops with limited registered options. Several crops have limited to no in-crop options because of lack of crop tolerance, low acreage numbers (minor use only) or because of weed resistance to certain groups, such as Group 2-resistant kochia and cleavers in peas and lentils. What’s more, some available herbicides for spraying peas and lentils can set the crop back. Spraying between the rows could reduce burning the crop, said Wolf.
Wolf is currently involved in dose-response studies to find out the different susceptibilities of crops to a variety of sprays and spray directions. When new herbicides and applications methods are tested, dose-response trials help determine how the crops react to them. Crops may react differently when the herbicide is sprayed beside them or over the top of them, rather than directly on them in a broadcast application, said Wolf. Dose-response trials also show how the weeds react to different doses applied in different locations. Identifying correct nozzles and their applications may help producers spray in stable, narrow patterns.
Nozzle selection
Wolf’s team has also looked at some problems with changing pressure when spraying, a problem common with all types of nozzles. The team has also been experimenting with angles for spraying. Modern sprayers are not designed to spray at the same pressure and change when travel speed changes in order to allow the spray rate to stay constant. The research team tried to rotate the nozzles and angled them to change spray patterns, which worked to help increase precision.
Wolf thinks a mechanical element will be needed to help precision spraying improve. Centimetre accuracy autosteer will be crucial, he said. The height and angle of the nozzle will need to be investigated and may need to be controlled using precision engineering solutions. Movement and drift of spray over small distances will also need to be researched. Trials on spraying between rows will be conducted in the summer of 2011.
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“Timelyremovaliseverythinginweedcontrolandit’sevenmoreimportantindiseasecontrol.Agoodsprayappliedatthewrongtimedoesn’treallydoitsjobatall.”
TOM WOLF
