Being with Extension for 20 years I have had the pleasure of calibrating numerous sprayers. I have calibrated anything from mules pulling a sprayer to small back pak sprayers to 100 foot spray monitor driven sprayers. I can say that the most common problem I encountered is improper nozzles or nozzles not matching on the sprayer. Some County Agents in Oregon found 86% of the sprayers calibrated by agents to be in need of adjustment and those in need of adjustment were due to failed spray nozzles. In many cases where pesticides fail the sprayer is the main issue. One farm had repeat failures of a product and a simple boom height adjustment resulted in no more problems. Here are some brief pointers in the proper calibration of sprayers. A fact sheet on Calibration of Sprayers is available at the Extension office. If you need specific assistance do not hesitate to call me or a local agent or crop consultant for help.
1. Pesticides are dangerous….wear rubber gloves and coveralls to complete this operation.
2. Take all nozzles and screen devices off sprayer (this includes the agitation nozzles inside the tank) and clean in soapy solution
3. With nozzles off ,run water through the whole system.
4. Check all parts for cracks. Pay attention to hoses and replace damaged hoses as needed.
5. Consider low drift nozzle replacement. Standard flats will lose 25% of spray to drift able fines while new air induction nozzles will lose only 1% to drift able fines.
6. Be sure that screens, washers, and tips are replaced in each of the nozzle bodies. A missed screen can result in a 25% over spray for that nozzle.
Calibration (This is the simple form and is highly accurate)
1. Measure spacing of nozzles and refer to the chart for the course length.
2. Measure off the course length on a typical soil surface you plan to operate the sprayer. Use bright colored markers to mark the ends.
3. Fill the sprayer halfway with water and hook to the tractor or mules you plan to use to spray with
4. Travel at a speed you are comfortable spraying at and operate the tractor and sprayer together without the pump running between the course flags.
5. Use a time piece to determine how long it takes to run the course. Do this three times to gain an average speed in seconds.
6. With the sprayer on a level surface turn pump on and begin spraying in place. Adjust pressure regulator to desired output. Start at 40 psi.
7. Collect with a device that reads ounces for the same time it took to run the course.
8. Ounces equals gallons per acre
Tee Jet References
1. For new sprayers and at least once per year all nozzles should be checked for even output. Either catch water for a set amount of time or use a flow meter to determine the output of each nozzle. On rate controlled devices this is the most crucial part of the calibration.
2. If a single nozzle is out of flow with the others by 10% replace the nozzle. This can occur with brand new nozzles so it will need to be done whether old or new.
3. If error in rate is <10%, or Adjust travel speed, if error in rate is >10% but less than 25%, or Change nozzle size, if error in rate is >25%
4. Pressure must be increased 4X to double sprayer output
5. Twice the speed = one-half the output
6. If you plan to use other than water for a carrier you will need to adjust the volume of water up to compensate for the differences in the density of the carrier. For instance liquid nitrogen weighs 11 lbs versus water at 8 lbs so if the desired output is 20 gallons per acre of UAN then the calibration with water would be about 22 gallons of water. Spray rate controls will require you to enter the correct conversion factors which are contained in many sources of spray nozzles and user guides.
On a typical 100 acre farm spray bill simply by calibrating $500 to $1000.00 can be saved by preventing over application which reduces the amount of pesticide in the environment and ensures proper application rates for efficient performance from a given product.
Tip: Instead of placing 50 or 100 mesh screens at each nozzle place a large in line screen that leads to each boom section thereby allowing for easy cleanout between batches.