Calibration

Calibration Challenge #1

• A label may call for 1 pint of pesticide to be applied over an entire acre (1 pint per acre).

• An acre is 43,560 ft2. (208 ¾ ft x 208 ¾ ft)• Some labels call for as little as ½ or 1/10 of an

ounce of dry material (WPs) per acre.

• How can this be done?

Dilution is the Solution

• 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

Calibration Dilemma #2How much pesticide do I add to the

tank?

• You will need to know:– How many gallons it takes your sprayer to

cover one acre…..Gallons per acre or GPA ?– How many acres you can spray with a

certain volume?– What is the labeled rate of the pesticide?– Make the dose calculation (how much do I

add to the tank)

Calibration Tip

• Keep everything constant.

• When you are field spraying, use the same speed, sprayer pressure and nozzle type as you did when you calibrated.

• Keep a calibration log.

Checking your Field Speed

• Set out a 200 foot course.

• Drive the course at a comfortable and practical field speed.

• Use this formula to double check your speed

• MPH = 136.4 Ex: 136.4 = 5 MPH Time* 27 sec.

* Time = seconds it took to drive the course

Determining GPA3 methods

• Calibration Strip Method– Preferred

– Most accurate

• 5940 Method

• 128th acre method

But first….Determining GPA

with a backpack or hand sprayer 18 ½ feet

18 ½feet

Measure out an 18 ½ by 18 ½ foot square in an area similar to what you will spray

Backpack - GPA

1. 18 ½ x 18 ½ foot square2. Spray & time yourself3. Spray into bucket for same time and using same pressure.4. Collect in Ounces5. Ounces = GPA6. Why does this work?

• 18 ½ x 18 ½ feet = 342 ft2 which is 128th of an acre

• There are 128 ounces in a gallon

Backpack GPAExample

• Sprayed calibration square and it took 45 seconds

• Sprayed into bucket for 45 seconds and collected 64 ounces

• GPA = 64

Calibration Strip Method

• Take a small area and relate it to an acre

• Need to know area of calibration test strip (in acres). One acre = 43,560 ft2

• Amount of liquid sprayed over strip

• Remember:

G---gallons applied per strip

P divided by

A ---acres in test strip= GALLONS PER ACRE

Calibration Strip MethodExample:

• Calibration strip is 66 feet x 66 feet or 4,356 ft2 43,560 ft2 = 0.10 acres

• 3 gallons applied per strip

• 3 gal/strip 0.10 acres = 30 GPA

Boom Sprayers• No matter what method of

calibration is used, you need to….– check nozzle spacing

– check output across the boom.

Checking Nozzle Spacing & Height

Nozzle Orientation

Nozzle output

Checking Nozzle Output

20”

Remember!Check Nozzle Spacing

Then……

Nozzle 1 Nozzle 2 Nozzle 3

51 oz 50 oz 42 oz

Check Nozzle Output For a Given Amount of Time! (usually 1 minute)

•Nozzle 1 = 51 oz

•Nozzle 2 = 50 oz

•Nozzle 3 = 42 oz

143 oz ÷ 3 = 48 oz. (average)

Checking Nozzle Output

• The average of all the nozzles is 48 oz.

• This is the benchmark you use to determine which nozzles need to be replaced or cleaned.

• A 5% error on either side of the average is commonly used.

Calibration Tip

• 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 50.4

– Any nozzle output between 45.6 and 50.4 is OK!

Boom Sprayer Calibration Strip Method

• Need swath width (W) x Course length (L)• Gives you sq. ft (ft2) of the test strip• Find acreage of the test strip

(test strip ft2 43,560 ft2)• Find liquid applied per strip (gallons)• Use simple math

Gallons applied per strip = GPATest strip in Acres

Keep going for example

Using test strip

Collect from each nozzle using test strip time.

Or you can refill the sprayer and note how many gallons it took

Figure your GPA• Example:

– Swath width is 35 ft– Course length is 200 ft– Calibration strip = 7,000 ft2 (35 x 200)– Test strip is 0.16 acres (7000 ÷ 43560) – You collect from all the nozzles or refill the tank

• 4 gallons is collected

– 4 gallons ÷ 0.16 acres = 25 acres

Broadjet

34

100 3400 = 0.078 acres 43560

0.5 gin 13 sec.

0.5 g 0.078 acres = 6.4 GPA

5940 Method

• Based on nozzle output within 5% of the average.

• Not only gives you GPA but also how much you need to collect from under each nozzle to reach a desired GPA.

• Uses the following basic formula:

GPA = GPM X 5940

MPH X W• 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 or

2) width of a broadjet swath in inches.

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 W 5 MPH x 20 100

GPA = 29.70 or 30 GPA

Using 5940 to find out how much you need to collect to get a certain GPA!

• Rearrange the basic formula to look like this:

GPM = GPA x MPH x W

5940

5940 Example #2• You want to apply 20 GPA.Your broadjet has a

swath of 35 feet. Your field speed is 5 MPH GPM = GPA x MPH x W

5940

GPM = 20 GPA x 5 MPH x 420 (35 ft x 12”)

5940

7 GPM = 42,000

5940

You need to collect 7 GPM to get 20 GPA

Boom Sprayer GPA128th Acre Method

• Measure distance between nozzles.• Use chart for test course distance. • Nozzle output must be close to uniform• Ounces collected from one nozzle = GPA

Nozzle spacing (in.) Test Strip (ft) 20 204 * *340 ÷ spacing (ft)

30 136 36 113 38 107 40 102

Broadjet -= 128th Acre Method

• Measure swath width• Set calibration course Swath width Course length 35 156 * *5460 ÷ W (ft)

40 136 45 121

• Time yourself• Collect for same time• Pints collected = GPA

Boom Output and GPA

Using the 128th method you get:

15 ounces = 15 GPA

Check the label

May be too low.

How many acres can you spray.

Volume used = Acres

GPA

How many acres can you spray - Example

• Have a 1000 gallon tank. Only want to apply 500 gallons.

• GPA = 25• 500 gallons = 20 acres 25 GPA• Backpack 5 gallons = 0.078 acres 64 GPA

Acres - Example 2

• Suppose you only want to spray 10 acres.

• GPA = 25 (25 GPA)

• Now just back-multiply….

Gallons??? = 10 acres

25 GPA

• 25 GPA x 10 acres = 250 gallons of total mix is needed (pesticide and water)

Dosage Determination

• Listed rate per acre …Read the label

• Lbs. of a.i. per acre– Liquid – % W.P.

Listed Rate Per Acre

• Acres x labeled rate = dose

• 10 acres x 1 pint/acre = 10 pints in a given volume– 300 gallon mix = 10 acres

30 GPA– 10 acres x 1 pint/acre = 10 pints– 10 pints of product to make a 300 gallon mix.

Pounds per Acre - LiquidExample – 1 lb of a.i. is recommended per acre

1 gal. Formulation x 1 lb a.i = 0.5 x 1 = 0.5 gal formulation/acre

2 lb a.i. Acre

Rate = 1 = 0.5 gallons formulation/acre

Lbs. a.i./gallon 2

Dry Formulations• 2 lbs per acre of an 80% WP is prescribed

1 lb formulation x 2 lb a.i. = 2.5 lbs formulation/acre

0.80 lb a.i. Acre

Rate per acre = 2 lb a.i. = 2.5 lbs

% a.i. 0.80

How much product to add to tank.

• Rate/acres x acres treated

• Example:

1 pt/acre x 10 acres = 10 pints.

• Backpack 0.078 acres x 16 oz. = 1.2 oz.