Selecting the best nozzle to get good coverage could increase yields by over 0.5t/ha in serious yellow rust situations, Agrovista trials have shown.


Trials were set up last spring to evaluate application effects on fungicides, following on from similar work with blackgrass herbicides.

The first project looked specifically at nozzle effect on fungicide performance across four varieties – Oakley, Robigus, Humber and Zebedee, explains Mark Hemmant, the firm’s technical manager.

Both Oakley and Robigus were hit hard by yellow rust. “There was active yellow rust at application in both.” Humber and Zebedee had less disease.

Each variety was sprayed with Proline (0.6 litres/ha) at flag leaf using one of four different nozzles (see table) in a replicated trial. All were blue 03 nozzles that could spray at a water volume of 100 litres/ha at a three-bar pressure with a forward speed of 14 km/h.

Yield response from nozzle choice

Nozzle

Robigus (t/ha over untreated)

Oakley (t/ha over

untreated)

Flat fan

+ 5.5t/ha

+ 5.35t/ha

Flat fan (angled forward 30 degrees)

+ 6.1t/ha

+ 6.1t/ha

Billericay air inclusion

+ 5.5t/ha

+ 5.6t/ha

Guardian Air (angled backwards)

+ 5.2t/ha

+ 5.8t/ha

Water-sensitive paper was placed in the upper, mid and lower parts of the canopy to check for coverage.

“Compared with a standard flat fan it appeared that angling the nozzle forward 30 degrees gave better coverage in all parts of the canopy,” Mr Hemmant says.

But for the two air inclusion nozzles, which give a coarser spray and reduce drift, coverage was not as good.

Getting good coverage is important when attempting to control yellow rust, Mr Hemmant says. “Angling probably helps to get the spray down the canopy, which would have helped control the active rust present.”

The angled flat fan gave a yield response of an extra 0.6-0.7t/ha over the standard flat fan. Perhaps not surprisingly, given their poorer coverage, the air inclusion nozzles didn’t reach those standards.

But the yields, particularly in the Oakley, weren’t poorer than the standard flat fan – a bit of a surprise considering the water-sensitive paper results.

Under less disease pressure in the Humber and Zebedee there were only marginal differences between nozzles.

The results suggest that in high yellow rust pressure, particularly with active disease, angling a flat fan nozzle might be a good idea, he concludes. “But I’m not saying don’t use an air-inclusion nozzle. It will give more spray days than a flat fan, and getting your fungicide timing right is important – from our timing work we’ve seen, each day you delay yellow rust control costs 50kg/ha/day in yield.”


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