Calibration
How much pesticide do I add to the tank?
• Gallons per acre or GPA
• How many acres can we spray with a certain volume
• What is the labeled rate
• Dose calculation (how much do I add to the tank)
• Calibration Strip Method
• Single Nozzle Method
• 128th acre method
But first….Determining GPA
with a backpack or hand sprayer 18 ½ feet
18 ½feet
Backpack - GPA
• 18 ½ x 18 ½ foot square
• Spray & time yourself
• Spray into bucket
• Collect in Ounces
• Ounces = GPA
• Why does this work?
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 small area (calibration strip)
• Amount of liquid sprayed over strip
• Number of strips in an acre
• One acre = 43,560 ft2
Calibration Strip Method
• 66 feet (swath) x 66 feet (calibration strip)• = 4,356 ft2
• 43,560 ft2 = 10 strips
4,356 ft2
• 3 gallons per strip• 10 strips x 3 gal/strip• GPA = 30
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……
51 oz 50 oz 42 oz
Check Nozzle Output!
Output should be within 10% of the average of all the nozzles
• Nozzle 1 = 51 oz• Nozzle 2 = 50 oz• Nozzle 3 = 42 oz 143 oz
143 oz 3 = 48 oz 4.8 or 5
43………48……..53 maybe 45½…48….50 ½ Check Nozzle # 3 Check Nozzle 1& 3 Recheck Recheck
10% 10%
10%
Nozzles Output in Ounces 21 Seconds
1. 14.0
2. 13.0 ***** 3. 16.0 4. 15.0 5. 15.0 6. 15.0 7. 14.0 8. 15.0 9. 16.0 10. 16.0 149.0
Average = 14.9 or 15 ounces
+10% = 16.5 ounces -10% = 13.5 ounces
Boom Sprayer Calibration Strip Method
• Need swath width (W)
• Course length (L)
• Number of strips in one acre
43,560 ft2
L x
W
Amount of liquid applied per strip
Using test strip
Collect from each nozzle using test strip time.
Figure your GPA• Example:
– Swath width is 35 ft– Course length is 200 ft– Calibration strip = 7,000 ft2 (35 x 200)– There are 6.22 strips in one acre (43560 ÷ 7000)– You collect from all the nozzle into one bucket
• 4 gallons
– 6.22 x 4 = 24.88 or 25 GPA
Broadjet
34
100 43560 = 12.8 3400
0.5 gin 13 sec.
12.8 x 0.5 g = 6.4 GPA
Boom-GPA
15 ounces = 15 GPA
Check the label
May be too low.
How many acres can you spray.
Volume used
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)
• 25 GPA x 10 acres = 250 gallons
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 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.
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