By Tracy Turner

With planting delays in some areas due to wet conditions, growers still have time to fine-tune and calibrate their sprayers to save money and protect the environment, according to Ohio State agricultural engineer and spray technology expert Erdal Ozkan.

“With the high cost of pesticides and fertilizers, growers who want to save money and spray chemicals as efficiently as possible need to make sure they fine-tune and calibrate their sprayers to work as accurately as possible, and get the job done with less use of chemical inputs,” Ozkan says.

The costs of those wasted chemicals can be high.

Farmers spend approximately $4.1 billion on pesticides annually, according to published reports. National surveys of field application results have shown that only about one out of three sprayers are applying pesticides at the recommended rates, while two-thirds are missing the mark by either over- or under-spraying, Ozkan says.

“In Ohio and other states, if we use an error margin of plus or minus 5% as the yard stick, nearly 50% of growers fail to get to that error margin,” he says. “If the intended rate and actual rate is different than that, then growers need to recalibrate their sprayer.”

According to Ozkan, of the 50% of growers who fail to obtain the 5% margin error, nearly half of them are over-applying their chemicals at an average rate of 23%.

“For example, if a grower has a $10,000 budget for chemical pesticides, and they happen to be in the group over-applying by 23%, that means they are throwing away at least $2,300 alone in that error,” he says. “And if they aren’t applying the right amount of chemicals, which could result in a larger economic impact because the chemicals may not work, the grower may have to reapply and their crops could suffer from yield loss.”

Tips for fine-tuning sprayers include:

  • Double-check your sprayer for mechanical problems before you start using. You won’t have time to do this when planting is in full swing.
  • Clean the sprayer tank thoroughly, and make sure nozzle filters are clean.
  • Clean spray nozzles, check their flow rates, and replace the ones that are spraying more than 10 percent of the original output.
  • Check the agitator in the tank to make sure it’s working properly.
  • Run water through the spray system to make sure everything is working properly.
  • Find out if the sprayer is delivering the proper application rate (gallons per acre).

While there are multiple ways to calibrate a sprayer, Ozkan says, growers should always measure the travel speed, measure the flow rate of the nozzle to ensure correct operating pressure, and check the system’s pressure gauge.

The following is typically the easiest way to calibrate for broadcast application that doesn’t require complicated calculations, he says:

  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.
  4. Drive through 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 the same pressure level and catch the output from each nozzle in a measuring jar for the travel time required 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% higher or lower than the average nozzle output rate, check for clogs and clean the tip, or 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 is equal to the application rate in gallons per acre: Average output (ounces) = Application rate (GPA).
  9. Compare the actual application rate with the recommended or intended rate. If the actual rate is more than 5% higher or lower than the recommended or intended rate, you must make adjustments.
  10. You can start the adjustments by changing the pressure. Lowering the spray pressure will reduce the spray delivered; higher pressure means more spray is delivered. Don't vary from the pressure range recommended for the nozzles that you use.
  11. You also can correct the application error by changing the actual travel speed. Slower speeds mean more spray is delivered; faster speeds mean less spray is delivered.
  12. If these changes don't bring the application rate to the desired rate, then you may have to select a new set of nozzles with smaller or larger orifices.
  13. Recalibrate the sprayer (repeat steps 5 through 12) after any adjustment.

For more information on sprayer calibration, see ohioline.osu.edu/aex-fact/0520.html.