What is the proper injection rate for a center pivot irrigation system that has a total rotation time of 20 hours and total volume of pesticide required is 28.4 gallons?

• A. 89.6 ml/min
• B. 120.0 ml/min
• C. 60.0 ml/min
• D. 45.0 ml/min

Answer: (A)

Calculating the injection rate means delivering a total volume over a given time, using consistent units. First convert the total pesticide from gallons to milliliters: 28.4 gallons × 3,785.41 ml/gallon ≈ 107,506 ml. Then convert the rotation time to minutes: 20 hours × 60 minutes/hour = 1,200 minutes. Now divide the total volume by the total time: 107,506 ml ÷ 1,200 min ≈ 89.6 ml/min. This rate matches delivering 28.4 gallons evenly over 20 hours. The other numbers would imply different volumes or times—for example, 120 ml/min over 1,200 minutes would require about 144,000 ml (≈38 gallons), not the given amount.