SPRAY TECHNOLOGY continues to develop apace, as this year’s farmers weekly/Syngenta Farm Sprayer Operator of the Year winner found when he visited France earlier this year.

Better boom stability for sprayers operating at up to 38m bout widths, drift studies to evaluate the merits of different nozzles and a sophisticated technique for mixing chemicals at the spray nozzles, to avoid tank mixing and reduce sprayer contamination, all impressed Michael Donnachie, sprayer operator at Ranston Farms, near Blandford Forum, Dorset.

At the CEMAGREF research centre near Montpellier in the south of France, a new wind tunnel with an in-built spray pattern checker is approaching completion.

It will allow the volume of spraydrift to be checked over a significant period at different wind speeds. The impact of head-on and following wind speeds, when operating at speeds of up to 20kph, will also be evaluated.

Such high spraying speeds, now increasingly common on commercial farms, also affect boom performance. A hydraulic vibrating platform has been built to check this under simulated field conditions.

Booms up to 38m wide are being evaluated at a range of speeds over a long period using cameras and infrared sensing.

“A boom that is OK at 8kph can be in trouble at higher speeds, or it may even perform better,” says CEMAGREF researcher Vincent Polveche. Potential problems include bounce, yaw, recovery to the correct alignment, and sheer metal or weld fatigue. “It’ll be good if the tests help manufacturers design out problems before we suffer in the field,” says Mr Donnachie.

Direct injection spraying, offering the potential to reduce tank and pipe contamination, also impressed. The idea is to mix chemicals and water as close to the nozzles as possible.

Such sprayers are already being commercially developed in France, with contractors evaluating models.

On-farm studies at the CTIFL Fruit and Legume Research station in St Gilles in the south of France have already shown that the approach can mix chemicals with an accuracy of +/-2%. “That is far more accurate than conventional sprayers,” says researcher Mathieu Vincent.

One down side is that the system is best suited to liquid formulations, although a tank is available for pre-mixing solid formulations.

Injection systems would tie in well with close-coupled chemical packs and GPS controlled differential applications, says Syngenta spraying specialist Tom Robinson.

Watch out for the 2005 Farm Sprayer Operator of the Year entry form in this week’s farmers weekly (p55) and in Crops Dec 11.