First UASS drift curves for agroforestry scenarios in Spain

Unmanned aerial spraying systems (UASS) allow the agricultural sector to execute precision spraying of plant protection products (PPPs). However, scientific knowledge regarding the spray drift generated by these aerial spraying systems is needed to facilitate their integration into European agriculture. Currently, UASS spray drift models have not been developed. This study aims to characterize sedimenting spray drift curves for UASS in 3D crops and compare them with reference drift models used in the environmental risk assessment of PPPs in Europe under Regulation (EC) No 1107/2009. To accomplish this, drift trials were conducted in typical agroforestry scenarios in Spain, including super high-density olive orchards, grapevines, and pine tree plantations. UASSs generated more drift than the terrestrial reference drift models in grapevine trials. Conversely, in super high-density olive orchards, the drift generated by UASSs was significantly reduced compared to both terrestrial and aerial reference models. For pine trees, a reliable UASS sedimenting drift curve could not be established. UASSs present a promising tool for agricultural applications, though with certain limitations. The similarity in drift between UASSs and the aerial reference model in grapevines may result from a wider-than-necessary swath width. Future developments of UASS should consider implementing variable-width spraying to match the target plant size. In forestry crops, the high spraying altitude complicated the development of a reliable sedimenting drift curve under the conditions of this study. Further research is needed to optimize UASS use in various agricultural settings. • First study to compare UASS sedimenting drift with EU aerial and ground models. • UASS drift in grapevines aligns with aerial reference models used in the EU. • In olive orchards, UASS drift falls between aerial and terrestrial models. • UASS drift follows a power equation, regardless of model or crop type. • Swath width is a key factor influencing UASS drift; optimization is needed.