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Calibrating Your Field Sprayer

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Calibrating Your Field Sprayer

Montana State University

Pesticide Safety Education Program

- Better Pest Control
- Environmental and human safety
- Effective use of time
- Inadequate control = more treatments

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

- 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

- Toxic spray equipment
- Clean with ammonia and water (2 quarts per 25 gallons)
- Rinse with water

- Replace nozzles, and filters

- Backpack Sprayer
- 128th acre method
- Long hand method

- Boom Sprayer
- Calibration Strip Method (Preset Distance)
- 5940 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

- Takes 10 seconds to spray 128th Acre
- In 10 seconds you spray 10 ounces.
- What is the GPA output?

10 GPA

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.

- 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

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

- 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?

- To find 5%
- Find your average…48 oz
- Move the decimal place one space to the left. 48. = 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!

- 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

- Conduct 2 or 3 times and get average
- Collect liquid from 1 nozzle for this amount of time
- Ounces of liquid collected = GPA

- Gallons applied per strip= GPA
- Test strip in Acres

- 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

- Determine how many acres that can be sprayed with a given GPA.
- Volume in Tank / GPA = Acres

- 2 pints / Acre
- You will be spraying 10 acres
- 10 pints of product

- 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.

- MPH = GPM * 5940 / GPA * W

- 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

- 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

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

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

- 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 20 100
- GPA = 29.70 or 30 GPA