Fruit & Vegetable Magazine

Equipment Spraying
Sprayer maintenance and nozzle selection

July 9, 2012  By Hugh McElhone

July 9, 2012 – The key thing for growers to remember with regards to sprayer maintenance is to ensure the sprayer is mechanically sound and liquid tight. It should also be safe to run down the road and the boom must allow for easy shutoff, says Helmut Spieser, agriculture engineer with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).

Sprayers need to be calibrated at the start of every season, and while farmers do not like to do this, they cannot rely on a rate controller to do a proper job. Rate controllers maintain precise sprayer output (GPA) but they do not calibrate your sprayer.

Always check nozzles for wear and spray pattern. Carry a couple of spare nozzles on the sprayer in case of a plug up. “A plugged nozzle should never come in contact with your lips,” he stressed. Use compressed air back at the shop for a thorough cleaning.


Growers should consider purchasing a wind meter to accurately measure wind speed and a compass to determine wind direction. These parameters should be recorded in your spray record every time you spray just in case someone challenges you. If there is a drift concern, and you end up in court, the Ministry of Environment (MOE) will want a (wind speed and direction) number, he advised.

Always maintain proper spray records, and have on hand the product label of what you sprayed, the MSDS sheet and the PCP number for that product. These contain the vital information needed by the Ontario Poison Centre (800 268-9017). Should some person be splashed, the Ontario Poison Centre will need that product number so they know how to treat injuries.

You should also have a spills kit on hand and display the phone number for the Spills Action Centre (800-268-6060).

When should you call the Spills Action Centre? Spieser said, for example, if a sprayer wheel spindle breaks while on the road and the leakage could fill your five-gallon pail in one hour, call the spills action centre. It is a minor spill but on a public road so call them promptly.

“Don’t worry about how much material has to spill before calling, just phone. That way the MOE knows your situation and what to expect when they get to the scene. You have to remember that MOE could get five or more calls from good Samaritans that could make the situation sound huge. But if you already called them then they aren’t going to get too worried,” he added.

For sprayer cleanup and clean out, rinse the sprayer daily after use so the product does not have time to adhere to the hoses, inner tank surfaces or nozzles. This recommendation is based on research conducted in the US 25 years ago that states daily rinsing removes 95 per cent of the product residue.

Always use fresh water and agitate for 10 minutes with the tank agitation system and tank rinse nozzles. “It should look like a dishwasher working in there,” he said. Spray the rinsate through the boom in the field you just sprayed. Be sure to remove and clean all screens and strainers. Thoroughly wash out the chemical inductor and any measuring containers. Pressure wash the outside of the sprayer, spray boom, tractor and tires to remove herbicides so, “you’re not a big wick weeder going into the next crop,” he said. If going into a sensitive crop, ensure you follow the label instructions for the proper rinsing regimen and use a cleaning agent.

Also consider removing the boom end caps to flush out product residue. A full wet boom does not slosh water around so residue will always be in the dead end of the pipe at the end cap, he warned. He then showed slides of a damaged tomato crop sprayed with what they thought was a ‘clean sprayer.’ The first 40 feet into the row were burned by the previous herbicide, and Spieser suspects it was due to the residue left in the end caps. This was a sprayer the researchers were using and thought clean.

On a self-propelled machine, with a 90-foot five section boom, there are up to 11 pipe sections with 22 end caps. To save time when flushing these pipe sections, Spieser suggests replacing the end caps with quarter turn ball valves. “Open them up while flushing individual boom sections with water and in a few seconds, it’s clean,” he said. These flushing valves may not come standard from manufacturers. He suggests growers buy the best machine for their operation and then modify it themselves with these clean-out valves.

To determine the wear of your spray nozzles, it is best to test the flow rate and spray pattern. “Manufacturers suggest replacing nozzles at 110 per cent of their rated flow,’” says Spieser. But if all nozzles have a consistent flow rate and the pattern is good, calibrate your sprayer and keep spraying, he advises.

If you have to change nozzles then you have to ask yourself what are your application priorities, namely; coverage, penetration, drift, and whether you are doing broadcast, directed or band spraying.

“You must also ask yourself what is the pressure capability of your sprayer, what are the crops to be sprayed, what are the pests, and what are the product modes of action,” he asked. Other concerns include carrier volume, the sprayer speed range and the type of boom you are operating, whether air-assist, electrostatic or conventional.

Such factors lead to determining the proper nozzle for your sprayer. Many growers have hollow cone, solid cone and flat fan nozzles readily available at home but there are also low pressure air induction and high pressure air induction tips available.

“All nozzles have three functions: they meter flow, make droplets and distribute droplets in a predetermined pattern, he said.” And the proper nozzle is needed to match your machine with the product and target to be sprayed.

“Depending on what you spray, droplet size matters,” he said, and there are now eight droplet size classification categories ranging from extremely fine to ultra coarse.

Fungicides and insecticides require a narrower droplet spectrum of fine-medium to medium for an effective spray. Herbicides, however, can be applied with anything from a medium spray or larger.

A major factor in nozzle selection is not only the product, and the capacity of the sprayer but the possibility of spray drift. The latest trend is toward the air induction nozzles simply because their significant drift reduction achieved by the production of larger droplets. Growers may need to adjust sprayer pressure to ensure drift reduction and/or effective crop coverage, says Spieser.

He recommends the following suggestions in nozzle selection:

  • calculate the size of nozzle required (GPA, nozzle spacing & travel speed)
  • determine the droplet size spectrum for the job at hand
  • choose a nozzle type that will deliver the spray quality at a reasonable pressure
  • evaluate the drift potential of your choice
  • select a different nozzle if necessary
  • conduct an evaluation of the coverage and penetration of the spray to the areas of concern in the crop
  • consider a nozzle that has a multipurpose capability

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