I hope everyone learned a little something at our calibration workshop held in Alma on February 27. I think it became clear as the day went on that we really need to spend more time going through examples and doing some hands-on calibration for everyone to get a good feel for what it means. One farmer mentioned to me a method he has used to calibrate his sprayer and I would like to share it as a no equations or calculations way for determining how much you are applying per acre. You simply need to mark off an acre in your field and apply water at the settings of tractor speed and nozzle pressure you will be operating at during an actual crop spraying. Measure the number of gallons of water you used and that is the gallons per acre you are applying. Another suggestion I received for checking individual nozzles on an airblast sprayer is to turn off all nozzles but one of the lowest ones and use that location to test nozzles from the other ports and check for flow rate. You can then insert each nozzle into the port, collect water for a minute to get the GPM for that nozzle. Then, take that nozzle out, put in another one and repeat until you have checked the GPM for each nozzle on the sprayer. This makes it possible to check nozzle output without getting wet from the other nozzles and makes it easier to collect water from nozzles that are normally in the upper part of the sprayer. When using this method, you may need to readjust the pressure after you close off all the nozzle ports but the one you are collecting from.
Please remember that cheap nozzles wear very quickly (up to 15% increase in flow rate after 40 hours of operation). Ceramic nozzles offer the best wear resistance.
There were a couple of questions asked during the workshop that I also wanted to address. First, the worksheet for the BOOM SPRAYER determines the gallons per minute required PER NOZZLE to obtain the desired GPA. The worksheet equation for the AIRBLAST SPRAYER provides the GPM for THE WHOLE SPRAYER (ALL NOZZLES) to obtain the desired GPA. Secondly, there was some question on where to obtain the water sensitive cards Dr. Brennan discussed during his presentation. Any retailer that sells nozzles may carry them. I suggest the 1” x 3” cards which are about $50.00 for a pack of 50. The cards are manufactured by TeeJet and sold by distributors. You may need to contact Teejet to find a distributor that sells them near you. You can reach Teejet at 630-665-5000. Thirdly, there was a question on where to get a water flow meter for easily measuring the amount of water to refill the tank when measuring the gallons used by the sprayer. Grainger is a good source for a wide selection of water meters. Grainger has a website at www.grainger.com or you can call them at 1-800-GRAINGER. Another source may be your local hardware and supply store. Do not forget fittings to connect your hose to the meter or a hose clamp if that will work. DO NOT use a fuel meter. They are calibrated for gasoline or diesel and will not work correctly with water.
Typical Flow Meter
Glen Rains, PhD, PE