A New Tool for Accurately Calibrating Your Air Blast Sprayer
Posted: March 26, 2012
Actual application rates in the field may vary from nozzle catalog values, because of pressure gauge error, wheel slip, speedometer error, and friction loss in the plumbing. The sprayer must be checked under actual operating conditions to adjust the pressure for the exact application rate required.
Applying a chemical at the wrong rate is disadvantageous. Using more than the desired amount of chemical is wasteful, may violate label rates, and may pollute the environment. Too low an
application rate probably will not be effective, and money will have been wasted on the material and its application.
Ideally sprayers should be calibrated at the beginning of the season, whenever nozzles are changed, or when changing the nozzle set up based on the crop and desired coverage. The challenge with air blast sprayer calibration is accurate and efficiently collecting and comparing the output from the individual nozzles. As a result, for the most part, growers often calibrate by determining how much spray material they had in the tank when they started the application and how much remained in the tank at the completion of the application and then dividing that amount by the total number of acres covered during the application. This method will tell growers an approximate gallons per acre for the application. However, it does not give an accurate picture of where the actual material was applied. For example, if that method indicated that 50 gallons per acre was applied, but there was a leak in a hose or somewhere else on the equipment, part of that “application” actually ended up on the ground. If one or more of the nozzles are clogged or worn, that fifty gallons per acre may not be accurately applied to the crops, and uneven application means uneven control of the pest population, which can lead to damage to part of the crop.
Finally, a solution is making its way to provide assistance to Pennsylvania growers. In the fall of 2010 members of the Penn State Pesticide Education Program attended an air blast sprayer calibration demonstration that provided a solution to the challenge of accurately capturing and comparing the output from airblast sprayer nozzles. A calibration tool, constructed by a Belgium firm, had seven individual collection tubes with hose that was connected to the tube on one end and the other end had a quick connect that attached to the individual nozzle on the air blast sprayer. After accurately calculating the ground speed that the applicator would be traveling and the pressure that the sprayer would operate during the application, the equipment is attached to the air blast sprayer. Once this is accomplished the equipment is operated as if an application is being made and the output from the nozzles is collected in the tubes. By simply viewing the output in the tubes it can be determined if nozzles are worn and putting out too much or if they may be clogged and as a result output is limited. Pre-calibration instructions and an airblast sprayer calibration worksheet are included with this newsletter. To arrange for someone to bring the calibration tool to your orchard to assist with calibrating your sprayer, please contact pested.psu.edu.