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OSU Extension

College of Food, Agricultural, and Environmental Sciences

May 7, 2019 - 8:02am --

Rainy weather has delayed our planting season, but one way to redeem some of the time is to make sure the field sprayer is ready to go when the weather breaks.  Weed pressure is a significant contributor to yield loss and weeds are enjoying a good spring.  Erdal Ozkan, OSU Extension Spray Technology specialist offers the following advice regarding a spring tune up for your sprayer.

 • Double-check your sprayer for mechanical problems before you start using it.  You won’t have time to do this when planting is in full swing. 

• Make sure the tank, the nozzles and nozzle filters are clean. 

• Check nozzle flow rates, and replace nozzles that are spraying more than 10 percent of the original output. 

• Check the tank agitator.  Make sure it is working properly. 

• Run water through the spray system and make sure everything is functioning correctly. 

• Find out if the sprayer is delivering the proper application rate (gallons per acre).  

 Sprayer calibration affects the effectiveness of pest control and the cost of crop production.  Applying too little pesticide may result in ineffective pest control, while too much pesticide wastes money, may damage the crop and increases the risk of contaminating the environment.  Calibrate the sprayer anytime there are changes in operating conditions and/or the type of chemical or product used is changed.  Calibrating a sprayer requires a watch showing seconds, a measuring tape, and a jar that measures ounces. The goal is to calculate the actual field application rate, or spray volume, in gallons per acre.

Erdal Ozkan, OSU Extension Spray Technology specialist recommends a method based on spraying 1/128 of an acre per nozzle and collecting the spray volume released during the time it takes to spray that area. This particular amount of land is chosen because there are 128 ounces of liquid in one gallon, making it easy to correlate the number of ounces sprayed on that small area to the number of gallons that would be sprayed on the whole acre. For example, if you catch 15 ounces from a set of nozzles, the actual spray volume rate of the sprayer is equal to 15 gallons per acre.

Accuracy depends upon making sure that the time measured to collect the spray from the nozzles is the same time that it takes to cover 1/128 of an acre. A table available at (Boom Sprayer Calibration) shows various nozzle spacings and the time you must travel to cover 1/128 of an acre for each spacing. For example, the travel distance for a 15-inch nozzle spacing is 272 feet; for a 20-inch nozzle, spacing is 204 feet; and for a 30-inch nozzle spacing, the distance is 136 feet.

To calibrate a boom sprayer for broadcast applications using this method, follow these steps:
1. Fill the sprayer tank with water.

2. Run the sprayer, inspect it for leaks, and make sure all vital parts function properly.

3. Measure the distance in inches between the nozzles. Then measure an appropriate distance in the field based on this nozzle spacing, according to the table in the boom sprayer fact sheet.  

4. Drive the measured distance in the field at your normal spraying speed, and record the travel time in seconds. Repeat this procedure and average the two measurements.

5. With the sprayer parked, run the sprayer at your operating pressure and catch the output from each nozzle in a measuring jar for the travel time determined in step 4.

6. Calculate the average nozzle output by adding the individual outputs and then dividing by the number of nozzles tested. If an individual sample collected is more than 10 percent higher or lower than the average nozzle output rate, replace the nozzle.

7. Repeat steps 5 and 6 until the variation in discharge rate for all nozzles is within 10 percent of the average.

8. The final average output in ounces you get is equal to the application rate in gallons per acre.

9. Compare the actual application rate with the recommended or intended rate. If the actual rate is more than 5 percent higher or lower than the recommended or intended rate, you must make adjustments.

            In addition to sprayer calibration to insure the correct spray volume, the sprayer operator also needs to select the correct nozzle matched to the pesticide or product.  Nozzles produce various outputs, droplet sizes and spray patterns.  Many pesticide labels contain information about nozzle requirements.  A very good publication entitled “Selecting the Best Nozzle for the Job” is available on line at

Anyone who would like a hard copy of either the sprayer calibration or the nozzle selection publications can contact the Wayne County Extension office at 330-264-8722.


Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.

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