1. Calibrating Your Field Sprayer
Montana State University
Pesticide Safety Education Program

2. Proper Calibration Offers
Better Pest Control
Environmental and human safety
Effective use of time
Inadequate control = more treatments

3. Calibrating your Sprayers
You need to spray 1 pint / Acre of Insecticide.
HOW?
Cannot just spread 1 pint over an acre without a carrier can you?

4. How much to dilute?
Its easier to spread 20 gallons of water (with 1 pint added) over 1 acre than it is to spread 1 pint by itself.
The goal…….
Find out how many gallons it takes your sprayer to cover one acre

5. Clean your Sprayer Toxic spray equipment Replace nozzles, and filters
Clean with ammonia and water (2 quarts per 25 gallons)
Rinse with water
Replace nozzles, and filters

6. Determine GPA (4 tools/methods)
Backpack Sprayer
128th acre method
Long hand method
Boom Sprayer
Calibration Strip Method (Preset Distance)
5940 Method

7. Backpack Sprayer (GPA) 128th Acre Method
Use water when calibrating
Use same nozzles and filters as when spraying
Measure an 18 ½ by 18 ½ ft area.
Spray area with water and time how long it takes
Constant speed and constant pressure
Spray water into a container for same amount of time.
Ounces = Gallons Per Acre Applied

8. Sample Scenario Using 128th Acre Scenario
Takes 10 seconds to spray 128th Acre
In 10 seconds you spray 10 ounces.
What is the GPA output?
10 GPA

9. Long Hand Scenario GPA for Backpack Sprayer
1 - If you have a different sized section that you spray
2 - Measure out known area sq ft / 43,560
3 - Spray known area and time yourself
4 - Spray into bucket for same length of time
5 - Measure amount sprayed and convert to gallons
6 - Multiply number found in step #5 times the number found in step #2.

10. Sample Scenario Long Hand Scenario
Known area is 66 x 66’ (4,356 sq. ft)
43,560 / 4,356 = 10
It took you 2 minutes to spray area
Collect 4 gallons in 2 minutes
4 gallons * 10 = 40 gallons per acre

11. Boom Sprayers
No matter what method of calibration is used, you need to….
check nozzle spacing
check output across the boom.

12. Check nozzle spacing and height

13. Boom Level or Nozzle Angle Correct

14. Worn Spray Tips

15. Verify that all nozzles are equal

16. Nozzle Output Check nozzle output for 1 minute and get average
If each nozzles output is not greater or less than 5% off of average, all is well.
How?

17. 5% error level To find 5% Find your average…48 oz
Move the decimal place one space to the left = 4.8 This is a 10% error
Divide by 2 = 2.4.
This is 5% error
Now add 2.4 to 48 for +5%
Subtract 2.4 from 48 for
5% Error range = 45.6 and 50.4
Any nozzle output between 45.6 and 50.4 is OK!

18. GPA for Boom Sprayer cont..
Nozzle output is same.
18” = 227’ course length
20” = 204’ course length
30” = 136’ course length
40” = 102’ course length
Or 340 / spacing in feet
Drive course in gear and rpm you will use when spraying and time yourself

19. GPA for Boom Sprayer cont..
Conduct 2 or 3 times and get average
Collect liquid from 1 nozzle for this amount of time
Ounces of liquid collected = GPA

20. or GPA for Boom Sprayer can be calculated by
Gallons applied per strip= GPA
Test strip in Acres

21. Sample Scenario Boom Sprayer
18” wide nozzles, 6 nozzles
What to do?
Travel 227’ and time
30 seconds
Measure amount delivered in that 30 seconds
15 ounces in 30 seconds
15 GPA

22. How much pesticide to add to the tank
Determine how many acres that can be sprayed with a given GPA.
Volume in Tank / GPA = Acres
300 GALLONS / 30 GPA = 10 acres

23. How much chemical do you need?
2 pints / Acre
You will be spraying 10 acres
10 pints of product

24. 5940 method GPA = GPM X MPH X W / 5940 GPA = Gallons Per Acre
GPM = Gallons per Minute collected from a single nozzle (Make sure all nozzle are within a 5% range.)
5940 is a constant
MPH = Field Speed
W = 1) width between nozzles or2) width of a broadjetswath in inches.

25. What about field speed?
MPH = GPM * 5940 / GPA * W

26. Sample Scenario 5940 find speed needed
1 nozzle / minute output = 0.2 gallons
GPA needed is 20 GPA
Width of nozzles is 12”
MPH = GPM * 5940 / GPA * W
= 0.2 * 5940 / 20 * 12
= 4.95 mph

27. GPA is given or required! Need GPM for each nozzle!
Then you can purchase appropriate nozzles in GPM
Rearrange formula once again
GPM = GPA * W * MPH / 5940
GPM = 20 GPA * 30” * 5mph / 5940
0.505 or 0.5 GPM nozzles needed

28. Sample Questions You have an output of 20 GPA
You need to spray 300 acres
#1 - How much volume will you need?
6000 gallons
You need to apply 2 oz / acre of Warrior 1E.
#2 - How much do you put in tank?
600 oz of Warrior

29. Questions Continued
You are calibrating your hand sprayer and it took you 15 seconds to spray 1 18 ½ by 18 ½ ft area.
#3 – What is your GPA?
15 GPA
With this 5 gallon backpack sprayer, you intend to apply 1 oz / acre of product.
#4 - How much do you place in your backpack tank?
Can only treat 1/3 acre at a 15 GPA rate, so 1/3 rate or 1/3 oz

30. Questions

32. 5940 example
You have checked all your nozzles and the average is 64 ounces per minute (OPM). All nozzles are within 5% of this average.
64 OPM = 0.5 GPM (64 ounces ÷128 oz./gallon)
Your field speed is 5 MPH
Your nozzles are spaced 20”apart
GPA = GPM X 5940 = 0.5 GPM x 5940= 2970
MPH X W5 MPH x
GPA = or 30 GPA