Standardizing agricultural spray droplet size distributions

Authors: Fritz, Bradley - Brad; SUN, SUSAN - Croda; KRUGER, GREG - University Of Nebraska

Submitted to: American Society for Testing and Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2021
Publication Date: 11/3/2022
Citation: Fritz, B.K., Sun, S., Kruger, G. 2022. Standardizing agricultural spray droplet size distributions. American Society for Testing and Materials. http://doi.org/10.1520/STP164120210077.
DOI: https://doi.org/10.1520/STP164120210077

Interpretive Summary: Spray droplet size is one the most significant factors driving the success or failure of an application. As such, understanding how spray nozzles and tank mixtures impact droplet size is key to providing applicators guidance on proper selection and use. A number of programs were established recently to evaluate application technologies for their impact on drift and efficacy through modifications to applied droplet size. None of these programs have been widely accepted or adopted due to complicated protocols and a limited number of testing facilities. In response, new facilities were established at a number of private and commercial locations in the past several years, creating a need for updated protocols and data quality control measures to account for measurement biases. A method is proposed to adjust droplet size data to align with standard baselines using distribution data defined by a set of internationally recognized reference nozzles and pressures. Fitting measured size distributions from these reference conditions to probability density functions and comparing to established baseline density functions, a set of facility-specific adjustment factors are established. This adjustment process allows for absolute versus relative comparisons of droplet size data from multiple laboratories, removing one of the key hurdles in the success of these programs designed to guide applicators in the successful selection and use of agrochemical and application technologies.

Technical Abstract: Spray droplet size has long been recognized as one the most significant factors impacting the transport and ultimate fate of applied agrochemical products. As such, understanding the role spray nozzles and tank mixtures play in the atomization process is critical to providing applicators guidance on proper selection and use. A number of government and industry sponsored programs have launched in recent years that were designed to evaluate selected application technologies for their impact on drift and efficacy as a result of modifications to applied droplet size. These programs have yet to meet wide acceptance and adoption due to overly complicated protocols and a limited number of facilities available that have the required capabilities to collected the data with appropriate rigor and quality. In response to the needs of these programs, new facilities have been developed in the past several years within both academic and industrial institutes. There is a need for updated protocols and data quality control measures that account for instrumentation and measurement method biases and allow for absolute comparisons of collected size data. A method is proposed to adjust droplet size distribution data to align with standard baselines using distribution data defined by a set of internationally recognized reference nozzles and pressures. Fitting size distributions measured from these reference conditions to probability density functions and comparing to established baseline density functions, a set of facility-specific adjustment factors are established. This adjustment process allows for absolute versus relative comparisons between droplet size data from multiple laboratories, removing one of the key hurdles in the success of these programs designed to guide applicators in the successful selection and use of agrochemical and application technologies.