Cost-effective tracing techniques for the rapid characterization of spray deposition and drift through electrical conductivity and fluorescence

The investigation of the performance of agricultural sprayer through drift and deposition sampling directly on field is of extreme importance, especially in view of ensuring an effective and optimal administration of plant protection products (PPP), necessary to limit waste of products and damages to the ecosystems. This is however a time and resource-intensive activity, typically resulting in highly variable results due to the unpredictable and uncontrollable atmospheric and operating conditions under which sprayers usually operate. To minimize the measurement uncertainties while also simpli-fying the procedures and reducing costs, in this work we propose a deposition assessment protocol based on the spraying of two distinct tracer solutions, leveraging two well-known phenomena: one based on optical absorbance, and the other on electrical conductivity. Although the selected tracers, namely uranine and potassium chloride, are already extensively used in other applications for their non-toxicity to both bystanders and environment, very little is published about their use in spray drift applications; the results obtained on the test bench promise to reduce the experiment costs, simplify the measurement, increase the reproducibility and facilitate the test automation. A test bench for nozzles has been employed to deposit the solutions on a matrix of Petri dishes; the original weight of deposited material in each sample is used, after complete drying and redissolution in fixed amounts of DI water, to verify the conductivity-concentration and absorbance-concentration laws. The two analyses show promising correlations, justifying an extended test campaign through further experiments, more representative of the actual spraying systems.