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Handy tools

Boom spray calibration

Is the sprayer putting out what you think it is? Catch each nozzle in a jug, type in what you caught and see your real litres a hectare - and which nozzles need a look.

Measure between two nozzles. 50 cm ≈ 20 inches.

The speed you will spray at. 1 mph ≈ 1.61 km/h.

From the product label or your agronomist. 1 US gal/ac ≈ 9.35 L/ha.

How long you catch each nozzle for - 60 s is easy to time.

Your own tolerance, e.g. 10 %.

Optional, during the jug test. 1 bar ≈ 14.5 psi. 0 to skip.

Optional: mark out 100 m and time it at spraying gear and revs. 0 to skip.

Nozzle 1, 2, 3 … in order along the boom, separated by commas or spaces (up to 120). Leave empty to see only the target.

Your sprayer is putting out

81.3 L/ha+1.7% over your 80 L/ha
1 L/minneeded from each nozzle
1.02 L/minaverage you caught

Each nozzle (litres a minute)

123456
Fill in the jug
1,000 mL in 60 s from each nozzle
Nozzles to check
1 of 6 more than 10% off: nozzle 4
Speed for your target
15.3 km/h
Or pressure for your target
Enter your gauge pressure
Speed check
Optional: time 100 m
Link to these numbers

How to do the jug test

  1. Fill the tank with clean water only, set the pressure you spray at and run the boom until it sprays evenly.
  2. Hold a measuring jug under each nozzle for the same number of seconds (the jug test time above) and write down the mL.
  3. Type the readings in order along the boom. Fix or swap the flagged nozzles, then test again before you add any product.

How we work it out

  • Needed per nozzle: L/ha × km/h × spacing in metres ÷ 600. So 80 L/ha at 15 km/h on 50 cm spacing is 1 L a minute.
  • Real rate: the average L/min you caught × 600 ÷ (km/h × spacing in metres). Each nozzle is compared with that average.
  • Fixing it: the speed that gives your rate with these nozzles, or the pressure - flow changes with the square root of pressure. 100 m in 24 s is 15 km/h (360 ÷ seconds).

Big changes in speed or pressure change the droplet size and the spray pattern, so stay within the nozzle maker’s pressure range and the product label - change nozzles if you need to go further. Wear the protective gear on the label, even with plain water near chemical residue. This is arithmetic on your own numbers, not advice or a label rate. Nothing you type is stored or sent anywhere.

Sprayer calibrated?

Now work out how much of each product goes in every tank load, or convert a rate from gal/ac.

Spray tank mix calculator Farm unit converter