Blackgrass control could be improved by up to 10% by using Defy nozzles instead of a traditional 110-degree fan jet.

In Syngenta trials, control was boosted from 88% using conventional flat-fan nozzles to 97.5% when using Defy nozzles, which alternate spray backwards and forwards across the spray boom. In each case, equivalent 03-sized nozzles were used.

The trial was conducted using full-sized farming equipment to apply a pre-emergence herbicide mix of 4 litres/ha of Defy (prosulfocarb) + 0.4l/ha Liberator (flufenacet/diflufenican) in winter wheat.

“These results show that moving from a vertical spray to Defy nozzles, which produce a spray inclined by 40 degrees to vertical, could improve blackgrass control by 10%, even with this tank mixture,” said Syngenta application specialist Tom Robinson.

“Such improvements are important because they reduce the weed population that the follow-up spray has to deal with.”

The Defy nozzles spray pattern was developed to produce a more even spray coverage around clods.

Tests using water-sensitive paper attached to wooden blocks to simulate clods showed that alternating the nozzles ensured the droplets felll on the clods and the flat soil surface just after them, said Mr Robinson.

“This area might otherwise be shielded from the spray by the clod because of the forward motion of the sprayer,” he explained.

In addition, the principles Defy nozzles use have been shown to halve the amount of spray drift.

“They use a narrow fan angle of 83 degrees, rather than the more conventional 110 degrees,” said Mr Robinson.

“This means that, although they give best results at boom heights of 500mm from the target, they can also be used with modern sprayers, which may have a higher minimum boom height of 700mm.”

Besides pre-emergence use, Defy nozzles have been tested for later spray applications.

Growers can fit them for Defy but leave them in for Axial post-emergence grass weed control in wheat and barley, and for grassweed control in oilseed rape using Fusilade Max.

Defy nozzles are available in sizes of 03, 035 and 04, allowing spray speeds of 12, 14 and 16km/h respectively, Mr Robinson added.