Backpack Sprayer Calibration Worksheet
1. Divide 340 by the measured spray width to determine the calibration course.
Example: Spray width is 6 feet, therefore the course length is 57 feet.
340 ft / 6 ft = 56.6666, round off to 57 feet.
340 ft / ___ ft = ___ feet course length.
2. Tag a tree down the row that comes closest to the specified distance.
57 ft / 5 ft = 11.4, round off to 11 feet.
Course length in feet ___ / tree spacing in feet ___ = ___ trees to count off.
3. Take an average of two trips to determine the time it takes to spray the course.
Example: Based on trips that took 16 and 18 seconds each, the average time to spray to the 11th tree is 17 seconds.
(trial #1 ___ seconds + trial #2 ___ seconds)/2 = ___ seconds.
4. Collect spray in a cup for number of seconds it took to walk the course. Number of ounces collected = number of gallons per acre (GPA) being applied.
Example: After spraying into a measuring cup for 17 seconds, you collect 7.5 ounces of water. 7.5 oz. per 340 square feet = 7.5 gallons per acre.
__ ounces collected = ___ gallons per acre.
5. Divide amount of herbicide you wnt to apply per acre by the GPA.
Example: For application in April, recommended Roundup® rate is 8 ounces per acre.
8 oz per acre / 7.5 gal. per acre = 1.06 oz Roundup® for each gallon water.
___ oz per acre / ___ gallon per acre = ___ oz. Roundup® for each gallon of water.
6. Determine ounces of Roundup needed per 3-gallong backpack load.
Example: 1.06 oz. Roundup® x 3 gallons = 3.18, round off to 3.2 oz Roundup® per three gallons of water.
___ oz. Roundup® X 3 gallons = ___ oz. Roundup® per 3 gallons of water.
7. Convert to milliliters
Example: 3.2 oz X 30 milliliters per oz = 96 milliliters® of Roundup in 3 gallons of water.
___ oz X 30 milliliters per ounce = ___ milliliters of Roundup in 3 gallons of water.