Application Teach-In - Nozzle wear

We know that application technique can make a huge impact on the performance of control products - it can make the difference between an acceptable 95% control, and an exceptional 98% or more.

In a series of Q&A Teach-In sessions, GreenCast is drawing on the knowledge and experience of Syngenta Technical Manager Glenn KIrby, to hear about some of the practical tips and ideas that will enable sprayer operators achieve the best possible results that will help to make good turf great.

GreenCast: Today we are looking at issues with sprayer nozzle wear, so what's the key importance Glenn?
Glenn: With spray nozzles being the final point of delivery it's crucial that they are working accurately and efficiently, if we are going to keep the spray on target.

We frequently see sprayers on golf courses that still have the same set of nozzles as when they were delivered years before. It's not a problem if they have been well maintained and checked, but all too often they may be worn or been damaged.

Glenn Kirby - Syngenta Turf & Landscape Technical Manager

New operators should always ask the question 'when were the nozzles last changed' when they move clubs or grounds and start using a different sprayer. And all operators must remain vigilant for signs of nozzle wear and tear.

GreenCast: What sort of problems should operators be looking for?
Glenn: It's impossible to identify nozzle wear from a visual appraisal, but they should be regularly inspected for physical damage; a slight burr or rough edge on a precision molded nozzle will seriously affect the spray pattern.

One of the most common problems is when a nozzle has been knocked whilst the machine is parked in the shed, so what may have been fine when last used will cause a problem when you start spraying again; it's a good idea to inspect all the nozzles before you first fill up, whilst the machine is clean and dry.

GreenCast: So how often should operators look to check nozzles for wear, and why?
Glenn: All nozzles wear over time; the rate of wear being dependent on the amount of use and the products being applied. MAXX formulation fungicides, for example, create very little wear, but a coarse liquid fertiliser or iron products can cause rapid wear - low quality iron products can be like sandpaper going through the nozzle.

I would always recommend checking nozzle output at least twice a year, and possibly each month during busy spraying periods. One thing to look out for is if you expect to spray nine greens on a 200 litre tank, and you have run dry after eight and a half then the nozzles may be to blame.

GreenCast: So can you just recalibrate and keep going?
Glenn: There is certainly some opportunity to adjust output to get the right application rate if all the nozzles have worn evenly, but if nozzles wear too much then the spray pattern will be affected and that will influence the leaf coverage and the potential performance of products.

As the nozzle outlet gets larger the droplet size increases, which can lead to poorer leaf coverage. Compare an 04 and an 08 nozzle, where the orifice size is the primary difference, and the impact on droplet size is clear to see. From the Nozzle selction Teach-In we know we can use this to our advantage for some applications, but for others it could prove a real problem.

More typically, and of greater concern, is if one nozzle has worn more than others and is applying at a higher rate. Overall the machine may be applying the right volume across the four or six metre width, but if one nozzle is applying 20% more than others, for example, then some areas will be getting too much fertiliser that may cause scorch or striping, or if applying fungicides plants sprayed with the lower output nozzles may not be getting the vital protection they require.

GreenCast: What's the answer?
Glenn: Operators need to check the individual output from each nozzle and that it is consistent across all the nozzles.

When the machine has been fully rinsed out and washed down, set the pump running and collect the output from the first nozzle for 30 seconds; providing you have at least 100ml, note down the volume and repeat for each of the other nozzles - if you don't collect 100ml in 30 seconds, collect the output for longer until you have a realistic volume to measure and compare.

Repeat for all the nozzles along the boom, noting down the precise output from each. Then work out the average output per nozzle. If any individual nozzle varies from the average by more than 10% then overall spray accuracy can not be maintained.

GreenCast: Can you just change the worn nozzle?
Glenn: No, that would compound the problem because the new nozzle would inevitably have a very different output to the existing set. You do have to replace the whole set.

It may sound excessive, but with the value of the products being applied and, more importantly, the value of the turf being treated, the cost of a set of nozzles is a relatively low investment to assure accurate application.

Thanks Glenn.

So the summary is:

  • Question when the nozzles in your sprayer were last changed?
  • Check nozzles for signs of physical damage before use
  • Measure the output from each nozzle to identify wear
  • Replace the whole set if any nozzles are damaged or worn