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Maintaining Uniform Application For Sprayers
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Maintaining Uniform Application For Sprayers

Proper sprayer operation involves calibrating equipment often and documenting it each time.

By John Fulton
Extension Specialist, Biosystems Engineering
Auburn University
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Document Maintenance

Food safety has been brought to the forefront in peanut production.

Darlene Cowart, with Birdsong Peanut Company, readily admits that her passion is food safety, and she has worked very hard to help producers understand their role in the food safety arena.

“Food safety begins on the farm,” Cowart says. “And, growers are first link in the chain of food safety and quality.

“Peanuts should be viewed as a food ingredient rather than a commodity.”

Cowart and other industry leaders worked to develop Good Agricultural Practices for peanut production. Of those GAPs with the greatest impact on food safety, three of them relate to equipment calibration in some way: documentation and employee training; pesticide usage and equipment maintenance and sanitation.

Calibrate, Then Record

The most important area involves record keeping.

As Cowart explains, “The mantra here is, ‘If it’s not documented, it’s not done.’ This is a key for good management and food safety practices.”

Important documentation records include, but are not limited to: detail of prior farm ownership and cropping history; information regarding variety and plant date; crop management activities during the growing season; pesticide application information; worker training; fertilizer and soil amendment use history; pest reports from scouts or consultants; equipment maintenance and sanitation schedules.
Employee training should be conducted for pesticide application and worker safety; proper equipment calibration, maintenance and operation; and proper equipment sanitation.

“You can say, ‘Yes, I calibrate my equipment every year.’ But if it isn’t actually documented somewhere, then it’s not really done. If you were audited or someone asked to look at your records, then it won’t be considered as done if the details are not written down,” Cowart says. PG

Sprayer technology has rapidly advanced in recent years with new rate control systems along with technologies such as guidance and automatic section control. While these modern technologies can provide substantial benefits for farmers and/or sprayer operators, they do require proper setup, operation, calibration and maintenance.

The primary considerations include selecting the proper nozzles for a specific application, flow meter calibration and checking nozzle uniformity. These are critical to maximizing the benefits of technologies while also maintaining the necessary spray efficacy of products.

Check Flow Meter Rate
During recent on-farm visits, we found sprayers that were operating outside of 10 percent from the target application rate because of an incorrect flow meter calibration number being set in the controller. The flow-meter calibration number is something that needs to be routinely checked by the operator, especially when changing products.

The easiest method of checking is to place a known volume in the tank, spray this volume, and then check and see if the controller indicates the same amount of volume has been applied. If the applied amount is not within a few percent, then the flow meter needs to be re-calibrated. Sprayer and rate control manufacturers have good, detailed calibration procedures to ensure one establishes the correct calibration number.

Other procedures exist but consult your operator’s manual. If you find that this number is inconsistent during your check for a particular product solution, then call your dealer or manufacturer. Incorrect flow meter calibration can lead to additional problems.

Pressure Affects Droplet Size
Another area of concern is that most rate controllers are flow-based systems, meaning they control flow but not necessarily pressure. This type of control system needs to be well understood by operators, since pressure in these flow-based systems can vary during field operations.

In one example, we found that the pressure ranged from five pounds per square inch to 65 pounds per square inch during application in three fields. We had pressure spikes to more than 100 pounds per square inch at times. While this pressure fluctuation may not impact some applications, it can for applications where droplet size is critical for product efficacy as in fungicide application.

Pressure variations can also impact the risk of drift since these high pressure spikes normally occur when entering and exiting headlands. Along with sprayer operation, nozzle selection is important to ensure the product is applied correctly.

Other Considerations
These are just a few comments about proper sprayer operation. Be sure to review and follow the calibration procedures by sprayer and technology manufacturers. Don’t base this year’s setup on last year’s.

Make sure you are selecting the proper nozzles for the application at hand and expected sprayer operation in the field (e.g. ground speed). Ensure that a pressure sensor is easily visible to the operator so they can keep an eye on it while spraying. This feedback can be important so the operator can maintain the desired pressure range for a nozzle/setup combination. PG

For more information or links on this subject, visit the precision ag Web site at

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