Spray and economics assessment of a UAV-based ultra-low-volume application in olive and citrus orchards

Automation is a new frontier in specialty agriculture equipment. Specifically, unmanned aerial vehicles (UAV), machine vision and robotics will increasingly appear in sustainable agricultural systems. The use of small UAVs retrofitted with spraying systems allows precision aerial applications on small targets. These precision applications can result in significant cost savings and reductions in risk to operators during treatments. This paper presents a novel and practical design and development of a small application system capable of being mounted on an unmanned aerial vehicle for agrochemical spraying tasks and an analysis of the quality of the application and economic costs in olive and citrus orchards compared with those of a conventional treatment. Once the equipment had been developed, field trials in super-high-density olive and citrus orchards were undertaken to evaluate the spray deposition efficiency. For comparison with a conventional hydro-pneumatic sprayer, the field tests took into account parameters such as the applied volume rate, spray drift, application time and equipment costs and depreciation. The results obtained indicate that there was a 7 €/ha difference in the application costs between the aerial vehicle and conventional equipment. It is hoped that the conclusions of this work will serve as the basis for a debate about the existing legislation governing this type of aerial work, which can be beneficial in specific cases and should be carried out in a safe and legal manner.