Reprinted from The Nebline, June 2008
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Tom Dorn UNL Extension Educator Do you need to spot spray weedy patches in the lawn or pasture with a hand-held sprayer? We will discuss a simple step-bystep calibration procedure that ensures you applythe correct amount of pesticide to comply with the product label and so you will achieve satisfactory results. In order to apply the recommended amount of chemical through a sprayer, you need to know two things: 1. The quantity of total spray output you will be applying per unit of area, e.g., gallons per acre (GPA); and, 2. The recommended amount of product to apply per acre. I recently came acrossa simplified method of calibrating hand-held sprayers. This methodology works for calibrating either compressed air (pump up) sprayers or sprayers with a motor driven pump to create pressure (hand guns). The following procedure illustrates the steps required to properly calibrate hand-held sprayers. Most of the procedure is the same whether you are using a compressed air or powered sprayer.Italicized text applies only to compressed air sprayers.
5) Spray the test area in the manner you 1) Note the “full” would normally do when controlling mark on the spray the target pest and record the time in tank. There will seconds to treat the test area. be space above the 6) Pump up the pressure again and spray mark for compressed into a container for air. the same number of 2) Determine theuseseconds it took to ful volume of the “treat’ the test area spray tank by mea(step 5) and measure suring the volume the fluid ounces This spray tank of water needed to (fl.-oz.) caught in the holds 2 gallons fill an empty tank container. The numwhen full. to the full mark. ber of fl.-oz. caught 3) Using only water, fill the container in the container Spray in a to the full mark. will be equal tothe container for the same Start the motorized gallons of spray you number of pump or pressurize would have applied seconds. the tank, then test had you sprayed a the spray pattern. full acre (GPA). Add pressure and/ Determine the Amount of or adjust the spray Chemical to Add to the Tank tip until you are satisfied with the 7) Divide the useful capacity of the tank spray pattern. (step 2) by thespray output, GPA Test spray 4) Measure and mark (step 6) to determine the decimal pattern and a test area 18.5 feet fraction of an acre covered by each adjust tip. x 18.5 feet square tank of spray solution. Continued on next page
Measure Spray Output
Flags mark 18.5 feet square
Measure a test area 18.5 feet x 18.5 feet square. Then spray in the manner you would normally do and record thetime in seconds to “treat” the test area.
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8) Read the label to determine the volume of product recommended per acre. 9) Multiply the volume of product per acre (step 8) by the fractional acre covered per tank (step 7) to determine the amount of product to add per tank of spray.
• Note the full mark. (Step 1) • Tom measured the useful volume of the spray tank and found it to be two gallons. (Step 2) • Test spray pattern. (Step3) • He measured and marked a test area 18.5 x 18.5 feet. (Step 4) • He sprayed the test area and found it took 32 seconds. (Step 5) • He caught the output in a container for 32 seconds and measured 34 fluid ounces of water caught. This shows Tom was putting out the equivalent of 34 gallons per acre. (Step 6) • Each tank will cover 2 gallons / 34 gallons / acre = 0.059 acre (Step 7) • The product...