Assessment of spray drift potential reduction for hollow-cone nozzles: Part 1. Classification using indirect methods.

Spray drift is one of the main pollution sources identified when pesticides are sprayed on crops. In this work, in order to simplify the evaluation of hollow-cone nozzles according to their drift potential reduction, several models commonly used were tested by three indirect methods: phase Doppler particle analyser (PDPA) and two different wind tunnels. The main aim of this study is then to classify for the first time these hollow-cone nozzle models all of them used in tree crop spraying (3D crops). A comparison between these indirect methods to assess their suitability and to provide guidelines for a spray drift classification of hollow-cone nozzles was carried out. The results show that, in general terms, all methods allow hollow-cone nozzle classifications according to their drift potential reduction (DPR) with a similar trend. Among all the parameters determined with the PDPA, the V100 parameter performed best in differentiating the tested nozzles among drift reduction classes. In the wind tunnel, similar values were obtained for both sedimenting and airborne drift depositions. The V100 parameter displayed a high correlation (up to R2 = 0.948) with the drift potential tested with the wind tunnel. It is concluded that in general, the evaluated indirect methods provide equivalent classification results. Additional studies with a greater variety of nozzle types are required to achieve a proposal of harmonized methodology for testing hollow-cone nozzles.