Measuring spray droplet size from agricultural nozzles using laser diffraction

Authors: Fritz, Bradley - Brad; Hoffmann, Wesley

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 9/16/2016
Citation: Fritz, B.K., Hoffmann, W.C. 2016. Measuring spray droplet size from agricultural nozzles using laser diffraction. Journal of Visualized Experiments. doi:10.3791/54533.
DOI: https://doi.org/10.3791/54533

Interpretive Summary: Researchers and agrochemical product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels for both ground and aerial application scenarios. Accurate measurement of spray droplet size allow applicators to select spray nozzles and operational conditions to maximize on-target deposition and minimize spray drift. Researchers with the Aerial Application Technology Research Unit in College Station, TX conducted several cross-laboratory studies to build common sampling methods using laser diffraction equipment to help standardize sampling methodology. This work allows both experienced and new users of laser diffraction equipment to conduct experiments related to spray nozzles and formulation using a standardized methodology to minimize experimental error and generate data that applicators can use in their daily operations.

Technical Abstract: When making an application of any crop protection material such as a herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e. plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describe methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter- and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. These conditions tend to be limited, but have to potential to provide for poor data. Successful adaption of this method can provide for a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected.