Abstract
Spray drift assessment encompasses classification of the capacity of each sprayer/technology/setting combination to reduce or avoid the spray drift risk, as well as drift measurement to define buffer zones mandated during pesticide application. Compounding the challenge of these tasks is the great variability of field evaluation results from environmental conditions, spray application technology, canopy structure, and measurement procedures. This study, performed in Spanish context, evaluates the effects of different parameters on comparative measurements of ground and airborne spray drift employing the ISO22866:2005 protocol. Four configurations of air blast sprayers, derived from two fan airflow rates and two nozzle types (conventional and air-induction), were tested in orchard and vineyard at late growth stage. Spray drift curves were obtained, from which corresponding Drift Values (DVs) were calculated using an approximation of definite integral. Both sprayer settings and environmental variables statistically affect spray drift total amounts and result variability. PCA analysis showed that nozzle type and wind speed characteristics explained 51% and 24% of the variance, respectively. In particular, mean wind direction influence ground sediments (Pr < 0.01) and maximum wind speed strongly influence airborne drift value (Pr < 0.0001). The wind characteristics concealed the influence of adopted fan airflow rates on final spray drift assessment results. The effect of uncontrollable environmental conditions makes objective and comparative tests difficult.
Highlights
An important goal in pesticide application is adequate deposition on the entire canopy according to treatment specifications
The shape of the curves for ground deposition (Figures 6 and 9) and airborne spray drift measured at 5 and 10 m (Figures 7 and 10) indicated that crop canopy structure influenced spray drift amount at different sampling distances, and total drift amount based on observed Drift Values (DVs) (Figures 8 and 11)
PC2 count was robust for wind characteristics, especially on the minimum, maximum, and mean wind speeds registered during field trials
Summary
An important goal in pesticide application is adequate deposition on the entire canopy according to treatment specifications. The 2009/128/EC European Directive for Sustainable Use of Pesticide [3] represents bedrock EU legislation for all improvements pertaining to drift reduction and efficiency of pesticide application, including an overall definition and requirement for dedicated buffer zones [4]. Among the technical information contained in the NAP, minimum buffer zone widths and their relationship to different spray application techniques must be delineated (in terms of drift reduction or avoidance capacity). These requirements clearly indicate that drift measurement methodologies and classification schemes unique to each sprayer/technology, based on potential contamination risk, are essential tools
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