Comparison of Test Methods for Spray Deposition and Distribution by Unmanned Aerial Vehicle for Agricultural Chemical Spraying Application between Japanese Convention Protocol and ISO 24253 Protocol

HighlightsSpray deposition and distribution evaluations of UAVs were conducted.Spray distributions by the ISO and the Japanese protocol showed similar trends.The Japanese test protocol is useful as an evaluation method.A great benefit is its consideration of UAV-specific downwash and crosswinds.Abstract. For this study, evaluations of spray deposition and distribution on industrial unmanned helicopters and multi-rotor UAVs were conducted, respectively, according to the Japanese convention test protocol for UAVs and the test protocol for ground boom sprayers specified in ISO 24253 part 1. Using both the Japanese conventional protocol and the ISO 24253 protocol, spraying was conducted with 8 L per hectare with commercial UAVs. The amounts of tracer captured by collectors placed on the ground surface were measured and converted to the spray application rate per area. Results found for spray distribution by the ISO protocol exhibited similar trends to those obtained using the Japanese protocol. Results obtained from comparing the spray depositions of both test protocols indicated coefficients of determination R2 of the spray deposition measured values as 0.64 and 0.85, respectively, for helicopters and multi-rotors. Under the Japanese protocol, droplets on each of the five planes of the cubic collector were examined. More than 40% of the total droplets were observed on vertical planes because of downwash from UAV rotors, despite the crosswind effect during spraying. Therefore, one reason for differences in deposition values between these test methods was that the Japanese test protocol was able to capture droplets from the lateral direction with the cubic collector, which could not be captured using the ISO test. The Japanese test protocol, which measures the amount of adhesion using cubic collectors, is a useful and promising evaluation method that takes into account the UAV-specific downwash and crosswind effects. Keywords: ISO 24253 part 1, Japanese convention test protocol for UAVs, spray deposition and distribution, UAV pesticide application.