Calibrating Your Field Sprayers

Tractor Spraying in a Field
Sprayer Calibration
Did you know that by not calibrating your sprayer frequently enough, you could be
risking fines and/or loss of your crop?
Calibrating your sprayer means accurately determining how much pesticide you are applying.
If you apply more pesticide than the label allows, you are violating the law and could be fined
and/or have your crop destroyed. Calibrating at least once per season, preferably several times, is absolutely necessary to ensure accurate application rates and effective pest control.
Sprayer calibration is equally important for planter box insecticide applicators. Follow the
manufacturer's instructions for calibrating planters.
Calibration steps
There are different ways to calibrate a sprayer. These steps below are one method you can use.
Sprayer Calibration Test Course Chart
Before calibrating, check your sprayer manufacturer's instructions; some require a special procedure for sprayer calibration. Here are the tools you will need: a watch, measuring tape, measuring container graduated in ounces, tip tester (determines flow rate for each spray nozzle in gallons per minute or liters per minute) and flags or stakes for marking. Also, a pocket calculator may help with the math. Always start with a clean sprayer.
1. Fill your sprayer tank about half full with clean water.
2. Measure the distance in inches between nozzles.
3. In the field, mark out a test course that's the length
    corresponding to the distance between your nozzles.
    Use the chart on this page.
4. Taking a running start, drive the entire test course from
    start to finish lines, driving at normal speed. Time the
    number of seconds required to complete the course.
5. Keeping the engine RPM running at the same speed
    used on the course, park your rig and set the brakes.
6. Set your sprayer pump pressure correctly for your spray
    tip type and desired gallons per minute (GPM).
7. Using a tip tester or plastic container marked in ounces,
    collect water from a single nozzle for the same amount
    of time it took you to drive the test course. Repeat for
    each nozzle. If any one nozzle's output is 5%
    more or less than the others, replace it.
8. Once all nozzles are outputting within 5% of each
    other, the average amount of water collected per nozzle
    equals your gallons per acre (GPA) output for your rig.
    For minor changes in output, adjust your sprayer pres-
    sure to achieve the GPA recommended by the pesticide
    label. For major changes, either change travel speed or
    nozzle tip size and recalibrate.