Determination of spray drift and buffer zones in 3D crops using the ISO standard and new LiDAR methodologies

Spray drift generated in the application of plant protection products in tree crops (3D crops) is a major source of environmental contamination, with repercussions for human health and the environment. Spray drift contamination acquires greater relevance in the EU Southern Zone due to the crops structure and the weather conditions. Hence, there is a need to evaluate spray drift when treating the most representative 3D crops in this area. For this purpose, 4 spray drift tests, measuring airborne and sedimenting spray drift in accordance with ISO 22866:2005, were carried out for 4 different crops (peach, citrus, apple and grape) in orchards of the EU Southern Zone, using an air-blast sprayer equipped with standard (STN) and spray drift reduction (DRN) nozzle types. A further 3 tests were carried out to test a new methodology for the evaluation of spray drift in real field conditions using a LiDAR system, in which the spray drift generated by different sprayer and nozzle types was contrasted. The airborne spray drift potential reduction (DPRV) values, obtained following the ISO 22866:2005, were higher than those for sedimenting spray drift potential reduction (DPRH) (63.82%-94.42% vs. 39.75%-69.28%, respectively). For each crop and nozzle type combination, a sedimenting spray drift model was also developed and used to determine buffer zone width. The highest buffer width reduction (STN vs DRN) was obtained in peach (˃75%), while in grape, citrus and apple only 50% was reached. These results can be used as the starting point to determine buffer zone width in the countries of the EU Southern Zone depending on different environmental threshold values. Tests carried out using LiDAR system demonstrated high capacity and efficiency of this system and this newly defined methodology, allowing sprayer and nozzle types in real field conditions to be differentiated and classified.This work was partly funded by the Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya, the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF) under grants 2017 SGR 646, AGL2007-66093-C04-03, AGL2010-22304-04-C03-03, and AGL2013-48297-C2-2-R. The authors also wish to thank Mr. Antonio Checa (Randex Iberica, S.L.) for giving us free Albuz nozzles for the spray tests. Universitat de Lleida is also thanked for Mr. X. Torrent's pre-doctoral fellowship