18 June 1999

Sleeve booms merit closer look

Sleeve boom sprayers promised much when they first

arrived in the UK ten years ago. But since then

uptake has been modest. Mike Williams finds out

whether growers are missing a trick

SLEEVE boom sales into the UK started in 1989 with Hardis Twin System sprayer from Denmark and the Degania range from Israel, now distributed by Knight Farm Machinery. Claims for reduced drift and better spray penetration attracted considerable interest.

More companies soon moved into the market, including Kyndestoft with a kit system to add to a conventional sprayer, Danfoil sprayers, some Gem models – now part of the Case IH range, and the Rau range distributed by Kverneland.

One of the big selling points is the ability to reduce drift risk. This, makers say, is because the spray is trapped in the airstream which blows downwards from the sleeve or tube above the boom, carrying the droplets into the crop and reducing the risk that some may drift away in the wind.

Confirmation of the claims comes from trials in the UK and overseas. Danish trials with a Hardi Twin sprayer showed drift reductions up to 60%, allowing the Hardi sprayer to work in a 6.2m/sec wind speed with less drift than a conventional sprayer in a 4.6m/sec wind.

A study of average wind speeds in the spring over a 10-year period suggests the drift reduction offered by a sleeve boom Twin compared with a conventional sprayer would double the spraying opportunities in typical April/May weather conditions, the company claims.

UK spray drift data includes tests at Morley Research Centre, which used 12m Degania and Hardi Twin System sprayers on sugar beet. Drift was measured while they were spraying at 90litres/ha with an 8kph forward speed on beet plants at the 30% soil cover stage.

Drift measurements were taken with wind speeds of 3.0 and 6.5 m/sec, and the result was about 50% less drift. This, the Morley report points out, is sufficient to allow the air-assisted machines to continue working on days when wind speeds would cause drift from an ordinary sprayer.

Significant improvements

The Morley research also showed significant improvements in spray penetration through the crop canopy. This was also supported by tests in Denmark with a Hardi sprayer, which recorded increased spray retention on winter wheat with air assistance, with the lower parts of the plants retaining more when a medium quality spray was used. In potatoes there was improved spray application to both upper and lower leaf surfaces.

The biggest UK project comparing sleeve booms and other systems was a five-year study by ADAS, Silsoe Research Institute, the Long Ashton Research Station and the Scottish Centre for Agricultural Engineering, using HGCA funds. This provided more evidence for drift reduction, allowing fine sprays to be used from a sleeve boom with no more risk than a medium spray from a conventional sprayer.

The HGCA-funded trial also confirmed the improvement in crop penetration, although this did not appear to produce a significant improvement in biological control or crop yield.

In spite of endorsements from the research teams, sleeve booms appear to be increasingly regarded as specialist sprayers for broad-leaf crops rather than general purpose sprayers. That is confirmed by Bill Hayward of Hardi.

"We dont make many sales to cereal growers, although they can certainly benefit from advantages such as improved drift resistance and reduced spray volumes," he says. "The price difference puts some people off. A sleeve boom sprayer costs about 40% more than a comparable conventional sprayer, but the benefits can very quickly cover the extra cost."

Tom Robinson, applications specialist at Novartis, agrees that cost is one disincentive. "If the main aim is drift reduction there are other methods available which are a lot less expensive," he says.

Not whole story

But price is not the whole story, he warns. The fan for a 24m sprayer needs about 40hp, and that means using a bigger, heavier, more expensive tractor. Sleeve boom sprayers are also more complicated and demand a good operator for best results.

But there are extra benefits, he notes. "In my experience there is no other system which gives the biological results that I get with a sleeve boom sprayer, and nothing else achieves the same amount of air movement under the canopy to give good deposition on the lower leaves. I can always get better results when chemicals go through a sleeve boom sprayer, and the system also offer the possibility to reduce inputs." &#42