Calibration & Math
Accurate calibration ensures you apply the right amount of pesticide â too much wastes product and may be illegal; too little is ineffective. This topic covers the calibration process, area measurement, conversion factors (acres to square feet, gallons to ounces), calculating application rates, mixing ratios, and the mathematics behind spray volume and ground speed.
Study Guide: Calibration & Math
Review these sample questions before starting the practice test.
Q1: How many square feet are in one acre?
- A. 10,000
- B. 52,800
- C. 4,840
- D. 43,560 square feet â
1 acre = 43,560 square feet. This is also 4,840 square yards or about 0.4047 hectares. This number is essential for calibration calculations.
Q2: If a label calls for 2 pints per acre, how many ounces per acre is that?
- A. 32 oz (2 pints x 16 oz/pint) â
- B. 16 oz
- C. 24 oz
- D. 48 oz
1 pint = 16 fluid ounces. 2 pints = 32 fluid ounces per acre. Understanding volume conversions is essential for accurate mixing.
Q3: How do you calculate the amount of product needed for less than an acre?
- A. Use the full acre rate
- B. Use half the rate
- C. Guess
- D. Divide the per-acre rate by 43,560 and multiply by the area in square feet â
For areas less than an acre: (labeled rate per acre / 43,560 sq ft) x actual area in sq ft = amount needed. Or divide the area in sq ft by 1,000 and use the rate per 1,000 sq ft.
Q4: What is a "mixing ratio" and how do you calculate it?
- A. The ratio of water to tank size
- B. How fast to stir
- C. The proportion of pesticide concentrate to water as specified on the label, expressed as oz/gallon or percent â
- D. The ratio of two different pesticides
Mixing ratios specify concentrate-to-water proportions. If a label says 2 oz per gallon, and you need 50 gallons: 2 x 50 = 100 oz of product in 50 gallons of water.
Q5: If you need to treat 5 acres at 2 quarts per acre using a 100-gallon tank at 20 GPA, how much product do you add?
- A. 2 quarts
- B. 20 quarts
- C. 100 quarts
- D. 10 quarts (5 acres x 2 qt/acre) â
Total product = rate x area = 2 quarts/acre x 5 acres = 10 quarts. Total spray needed = 20 GPA x 5 acres = 100 gallons. Add 10 quarts of product to 100 gallons of water.
Q6: How do you convert parts per million (ppm) to percent?
- A. Divide by 10,000 (1% = 10,000 ppm) â
- B. Multiply by 100
- C. Divide by 100
- D. Multiply by 10,000
1% = 10,000 ppm. To convert ppm to percent: divide by 10,000. To convert percent to ppm: multiply by 10,000. Example: 500 ppm = 0.05%.
Q7: What is the "1/128 acre" calibration method?
- A. A method where ounces of output from one nozzle collected over 1/128 acre equals gallons per acre directly â
- B. A metric conversion
- C. A soil test method
- D. A spray pattern test
For a 20-inch nozzle spacing, 1/128 acre = 340 feet of travel. Collect output from one nozzle over that distance. The ounces collected directly equals GPA (since 128 oz = 1 gallon).
Q8: How do you calculate spray tank mix for a given area?
- A. Fill the tank and spray
- B. Add product first
- C. Total spray volume (GPA x acres) determines water needed; then add product at the label rate per acre for total acres â
- D. Use the same amount every time
Step 1: Calculate total spray volume = GPA x acres to treat. Step 2: Calculate total product = rate/acre x acres. Step 3: Add product to partially filled tank, agitate, finish filling to total volume.
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