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Talking Agronomy with Chris Martin: Making every drop count

Due to the dismal commodity prices constantly squeezing margins, it is vital we get the best possible performance from our fungicides this spring and two key areas to focus on are timing and application. 

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Talking Agronomy with Chris Martin: Making every drop count #arablefarming

I am convinced there is simply no room for error when it comes to timing. The flag leaf is still our most valuable ‘solar panel’ in a wheat contributing to about 50% of final yield.

When it comes to flag leaf spraying, our target is exactly that, the flag leaf, and it’s vital to get good coverage over the whole of the flag leaf to maximise fungicide performance. The optimum time is as soon as flag leaf is fully emerged (GS39). Any delay from here can be very costly.

Even in an average disease year like last year, Agrovista trials showed a delay of as little as a week from GS39 resulted in well over a tonne per hectare yield loss and in high disease year, losses can be significantly higher.

Going too early, e.g. GS37 (flag leaf emergence) can also be as costly as going too late, as there is very limited movement of chemical into leaf still to emerge, hence going before the flag leaf is fully emerged can leave the rest of the flag leaf unprotected.

While timing is of paramount importance, so too is application. It is widely accepted better coverage of the target generally provides better performance of the product.

See also: Top tips to improve fungicide efficacy

You have 64 times as many droplets using a fine nozzle with a droplet diameter of about 100 microns than a coarse one with droplet diameter of about 400 microns for the same water volume; hence the finer spray quality you can practically use on the day of spraying is likely to give the best performance.

This obviously has to be balanced with the increased risk of drift from a finer spray quality. In order to minimise drift risk it is important to have the nozzle as close to the target as possible while still achieving the correct spray pattern. As boom sizes and forward speed have increased in recent years in order to cover more acres, so to has boom height.

For most traditional sprayers the optimum height above the target should be 40-50cm, yet in reality most are 60-70cm. As boom height increases, the spray pattern suffers and drift increases rapidly. If you can reduce your boom height below 50cm it’s going to have a massive improvement on performance.

I’m also a big fan of the theory that angling nozzles and bringing lateral movement to spray droplets can further improve coverage. Angling nozzles does, however, increase the risk of spray drift by increasing the distance the droplets have to travel from the nozzle to the target. It has been suggested alternating the nozzles forward and backward along the boom could reduce this potential problem by providing a break in the spray sheet for air to pass through, however, we found at traditional forward speeds, the backward angled nozzle actually increased drift.

These findings led Agrovista to develop the configuration of angling every other nozzle forward 30 degrees while keeping every other nozzle straight down.

Not only does this reduce the drift potential from angling nozzles, but further increases coverage by bringing in two angles of attack. I am consistently seeing significant improvements in disease control and yield from growers adopting this nozzle configuration.

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