Picking the correct nozzle for a spray job can be a daunting task. There is a lot of product selection, and a lot of different features. We try to break the process down into four steps.
1. Identify Your Needs
Before making any assumptions about the right nozzle for you, review your needs and objectives. Are you trying to reduce drift? Do you want better coverage? Are you moving towards more fungicide application? Do you need a wide pressure range?
It’s always a good idea to review your experience with your previous nozzle. What, if anything, would you like to change?
2. Identify Flow Rates
Most spray operations fall into one of three categories, (a) pre-seed burnoff (3 to 7 US gpa); (b) in-crop early post-emergence (7 to 10 US gpa); (c) late season application to mature canopies (10 – 20 US gpa).
To find the right nozzle size, you need to know the application volume, the travel speed, and the nozzle spacing. Most sprayers have 20” nozzle spacing, but some have 15” spacing. Use these metric or US units charts to find the right flow rate for 20″ nozzle spacings. Various on-line calculators from Hypro, John Deere, TeeJet, Greenleaf, or Wilger or their apps, are also helpful.
In the chart, the top row lists water volumes. The columns contain travel speeds. Travel speed is somewhat flexible and can change throughout the field.
Let’s assume the water volume is 7 gpa, and the desired application speed is 14 mph. Move down the “7 gpa” column, searching for 14 mph. You will encounter 14 mph about 5 times: 02 nozzle @ >100 psi, 025 nozzle @ 70 psi, 03 nozzle @ 50 psi, and 035 nozzle @ 35 psi (the 035 size is only offered by the Hypro GuardianAIR).
Note that for the smaller nozzle sizes, the spray pressure is perhaps too high, and for the larger sizes, it is too low. Select a size that allows optimum nozzle performance and travel speed flexibility. In this example, the 025 size is optimal. The column for the 025 nozzle can now be used to predict the travel speed range from 30 psi to 100 psi, about 9 to 17 mph. For the 03 nozzle, the minimum speed would be 11 mph, too fast for some.
3. Select the Nozzle Model
For general spraying, select from these common nozzle models.
All have intermediate spray qualities (primarily Coarse), offering good coverage at reasonable water volumes and good drift control. In alphabetical order:
All nozzles should be operated near the middle of their pressure range, for air-induction this is 60 psi or higher. This allows maximum flexibility when travel speeds change or when spray quality is adjusted with pressure.
For fusarium headblight, consider a twin fan nozzle.
Keep your booms no more than 15” to 25” above the heads for best results.
For finer sprays (lower water volumes), simply increase spray pressure or consider a non-air-induced design.
For the best drift protection, consider these tips.
Although superior for drift control, they are not well suited for low volume or low-pressure spraying, nor for contact herbicides or grassy weeds, as spray retention and coverage may be poor.
Before making a selection, check the nozzle’s recommended pressure range and the spray qualities within that range from the manufacturer info. This will help you set a target pressure and identify your travel speed range.
4. Tweak and Confirm
Under field conditions, the spray pressures which produce the desired water volumes can vary from the charts. Make sure you trust your pressure gauge reading and know the pressure drop from the gauge signal to the nozzles. Add the pressure drop to your target pressure reading. If using a rate controller, use the pressure gauge as your speedometer to ensure optimal nozzle performance. Adjust travel speed until the nozzle pressure meets with your spray quality and pattern goals. Spray pressure is more important than travel speed – make your pressure gauge your speedometer.