Fluid Application Technologies in Plant Protection and Irrigation: A Review from Droplet Dynamics to Sprayers and Sprinklers

Plant protection and sprinkler irrigation rely on common fluid dynamic processes, including liquid atomization, droplet transport, target interaction, and flow distribution. This review analyses these mechanisms within a multi-scale framework. The analysis starts with droplet–target interactions. It addresses droplet impact and foliar retention in plant protection, alongside droplet kinetic energy and soil-surface responses in irrigation. The discussion then extends to the spatial transport and distribution of sprays. At the device scale, this work examines nozzles and sprinklers from the perspective of fluid mechanics and structural innovation, detailing how nozzle geometry and flow conditions affect macroscopic application performance. Finally, this review addresses advances at the system scale, with a focus on energy consumption and data-driven performance prediction. By connecting fluid behavior across multiple spatial scales, this work links micro-scale droplet dynamics to whole-system performance and identifies directions for improving agricultural spraying and sprinkler irrigation systems.