Measuring Spray Coverage – Tips #8

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About Jason Deveau (Spray_Guy)

Jason (@spray_guy) is the OMAFRA Application Technology Specialist. BSc (Biology and Psychology '96), MSc (Plant science '98), PhD (Plant cell electrophysiology '03). Jason studies and teaches methods to improve the safe, effective and efficient application of agricultural inputs. Co-administrator of Sprayers101, co-author of the Airblast101 Textbook, slow cyclist, slower runner.

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The importance of good spray coverage is emphasized in all kinds of agricultural publications, including product labels. But, according to Tom Wolf, “the labels are remarkably silent on what good coverage actually is and how you can actually measure it.”

Tom goes on to explain that spray coverage can be defined using three main criteria: droplet density, area covered and dose administered. In order to measure and assess spray coverage, we recommend using water sensitive paper, a rigid, specially-coated, yellow paper which is stained dark blue/purple by aqueous solutions. The paper can be positioned at the targeted levels of the crop canopy with a paper clip or other handy instrument and the coverage received in the field then compared to recommended levels produced in the lab to give an indication of whether or not coverage needs to be adjusted through increasing water volumes or altering droplet size.

Learn to integrate spray coverage evaluation into your spray operation, and how doing so can help you fine-tune applications.