Correct boom height helps eliminate spray drift
BOOM height is the most influential factor in limiting drift during spraying, new research work has confirmed.
Compared with other factors influencing drift such as droplet size, wind speed and sprayer forward speed, boom height issues have had a lower profile in terms of operator training and available information.
According to Professor Paul Miller of TAG’s Silsoe Spray Applications Unit, and research leader for a Chemical Regulation Directorate-funded project looking at factors affecting drift, doubling boom height (from an assumed starting height of 0.5m above the crop) could increase spray drift by between 5 and 10 times.
“The focus for operators until now has very much been on the other issues affecting drift such as forward speed and wind speed,” says Prof Miller, who calls for a greater focus on boom heights in the field and during operator training courses.
Prof Miller suggests many operators may think the forward speed of a sprayer is critical to the resultant spray drift, but he points out doubling a machine’s speed from 8km/hr to 16km/hr would not double the amount of drift.
“Other factors are still important but the research shows us boom height is key. We know boom height is important for grass-weed control in autumn and early spring, when we use a fine spray for better coverage of small grass-weeds, and it’s during this period of the season (up until a T0 timing) that attention to boom height is critical.
“There’s little in the way of a crop to help take out some of the drift, and operators are wary about damaging boom ends on the ground.”
Auto boom height systems could play an increasingly important role in reducing spray drift, particularly on spray booms of 24 metres and wider. “It’s the one thing where investment is always justified on any sprayer with 20m-24m boom widths or more, and it’s encouraging to see that increasing numbers of these systems are being employed,” says Professor Miller.
According to Bayer Crop Science’s Gordon Anderson-Taylor, Professor Miller’s findings back up the company’s concerns that application technique receives insufficient attention from growers.
“Boom height control is essential for maximising efficacy and reducing drift, but with so many growers operating huge spraying machines, the right height is difficult to maintain consistently.
“We’ve presented advice on correct boom height direct to growers this season. We regard it as a key part of the stewardship advice for Atlantis (mesosulfuron + iodosulfuron),” says Dr Anderson-Taylor.
Factors affecting spray drift in order of importance:
- The boom height of the sprayer
- The wind speed and droplet size
- Forward speed of the sprayer