Round-Robin Evaluation of ASTM Standard Test Method E2798 for Spray Drift Reduction Adjuvants

Abstract

Drift Reduction Agent has been defined in ASTM Standard E1519 Terminology Relating to Agricultural Tank Mix Adjuvants as “a material used in liquid spray mixtures to reduce spray drift.” ASTM Standard E609 Terminology Relating to Pesticides defines drift as “the physical movement of an agrochemical through the air at the time of application or soon thereafter to any non- or off-target site. Drift shall not include movement to non- or off-target sites caused by erosion, migration, volatility or wind blown soil particles that occur after application unless specifically advertised on the label.” Because there are many commercial tank mix adjuvants designed to reduce spray drift, there is a need to establish an ASTM Standard Test Method to evaluate their effectiveness. ASTM Standard E2798 is the new test method developed for the Characterization of Performance of Pesticide Spray Drift Reduction Adjuvants for Ground Application. This paper presents the data generated from the round-robin testing of this method. The method provides guidelines for the measurement of parameters pertaining to the performance of drift reduction adjuvants under simulated field application conditions. The measurements can be made in a wind tunnel or a spray chamber. The method describes the preparation, composition, and test/application conditions for droplet size, spray pattern measurements, and fines reduction. The exact selection of application conditions such as nozzle type and tank mix partner may vary according to the intended use conditions.

Measurement and classification methods using the ASAE S572.1 reference nozzles

“…A growing number of laboratories are incorporating droplet size measurements into both research and development of agrochemical technologies. Each laboratory has invariably developed their own sampling setup and protocols with ranges in both sampling distance from the nozzle and concurrent airflow velocities (Elsik 2011). Both have been shown to significantly impact the droplet sizing results from laser diffraction instruments, with concurrent air velocities less than 6.7 m/s over-estimating the volume fraction of the smaller end of the spray (Young and Bachalo 1988;Arnold 1990 andElsik 2011).…”

“…Each laboratory has invariably developed their own sampling setup and protocols with ranges in both sampling distance from the nozzle and concurrent airflow velocities (Elsik 2011). Both have been shown to significantly impact the droplet sizing results from laser diffraction instruments, with concurrent air velocities less than 6.7 m/s over-estimating the volume fraction of the smaller end of the spray (Young and Bachalo 1988;Arnold 1990 andElsik 2011). One method of addressing these interlaboratory differences is by using standardized spray nozzles as relative measures for classifying other nozzles or spray formulations.…”

“…A recent round robin study illustrated the potential differences in numerical droplet size data that exist between labs in which the labs use different evaluation protocols. Five labs, all using laser diffraction, but with differing coaxial air flows (four at 0.7 m/s or less and one at 3 m/s), evaluated droplet size for a series of nozzles and spray formulations (Elsik 2011). Labs using concurrent airflow of 3 m/s reported consistently larger droplet sizes and smaller percent volumes of less than 105 µm than the other labs (Elsik 2011).…”

“…Five labs, all using laser diffraction, but with differing coaxial air flows (four at 0.7 m/s or less and one at 3 m/s), evaluated droplet size for a series of nozzles and spray formulations (Elsik 2011). Labs using concurrent airflow of 3 m/s reported consistently larger droplet sizes and smaller percent volumes of less than 105 µm than the other labs (Elsik 2011). This is consistent with earlier work and was documented previously by a Spray Drift Task Force (SDTF) study (1997).…”

“…This study noted that spatial bias from laser diffraction results diminishes with higher air flows. Only one set of reference nozzle curve data with water, was presented by Elsik (2011). The study gave no indication of which lab generated the data.…”