Calibrating a Backpack Sprayer - Frequently Asked Questions

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 What is a backpack sprayer used for?
A backpack sprayer is an essential tool for most Market Gardeners. It can be used for spot spraying, as well as whole field spraying (for small areas). The backpack reduces the need for large equipment, and can be quite effective in chemical applications. Proper calibration can make a big difference, economically and environmentally.

Why calibrate properly?

  • Increased efficacy and efficiency in chemical application
  • Decreased costs for chemical products due to a reduction in the amount of required product
  • Decreased costs for chemical products due to a reduction in the number of sprays
  • Decreased environmental impact
What is the spray process?
  • Read the product label
  • Determine the volume to be sprayed
  • Calculate the amount of product required
  • Practice with plain water (2 passes) --> sets ground speed, increases uniformity
  • Put on protective gear and mix spray solution
  • Apply product as practiced
  • Rinse sprayer (dispose of rinse water appropriately) and clean up
What information is needed for calibration?
In order to properly use and calibrate a backpack sprayer, the following information must be known. Some of this information concerns the product to be applied, while the rest relates to the area to be sprayed.
  • Amount of active ingredient to applied per area (hectare or acre) [Pesticide Rate]
  • Amount of water to be applied per area (hectare or acre) [Spray Volume]
  • Area to be sprayed
How to calibrate a backpack sprayer?
Pesticide rate = millilitres of product per hectare (ounces/acre)
Area = # of rows X Spray width X Row Length
Total water to be applied = Area X Spray Volume
# of tanks = Total water to be Applied / Tank Capacity
Product / Tank = (Area X Pesticide Rate) / # of Tanks

Example Calculation (Metric): Decis 5EC
Area = 20m X 50m = 0.10ha
Total water to be applied = 0.10ha X 350 L/ha = 35L
# of tanks = 35L / 15L = 2.3 --> 3
Product / tank = (0.10ha X 150ml/ha) / 3 = 5 ml

Example Calculation (Imperial): Decis 5EC
Area = 60 ft X 150 ft = 0.21 ac
Total water to be applied = 0.21 ac X 31 gal/ac = 6.5 gal
# of tanks = 6.5 gal / 3 gal = 2.2 --> 3
Product / tank = (0.21 ac X 2.14 oz/ac) / 3 = 0.15oz

Prepared by Rob Spencer, Ag - Info Centre, Alberta Agriculture and Forestry.
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For more information about the content of this document, contact Robert Spencer.
This document is maintained by Marie Glover.
This information published to the web on June 18, 2004.
Last Reviewed/Revised on May 1, 2017.