EXPERIMENTAL DESIGN AND SAMPLING TECHNIQUES FOR EFFECTIVE EVALUATION OF SPRAY DRIFT

Authors: Smith, Lowrey; Mulrooney, Joseph - Joe; Elmore, Carroll

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 6/8/2000
Publication Date: 7/10/2000
Citation: Smith, L.A., Mulrooney, J.E., Elmore, C.D. 2000. Experimental design and sampling techniques for effective evaluation of spray drift. American Society of Agricultural Engineers Meetings Papers. Paper No. 001029.

Interpretive Summary: Spray drift can be defined as the movement of liquid spray droplets to areas outside the intended target zone. Such drift is influenced primarily by droplet size, wind speed, spray release height, relative humidity, and application rate. The study of drift management relative to specific treatments; which could include atomization technologies, equipment setup parameters or crop conditions; has proven to be difficult because of uncontrolled environmental factors that affect drift in addition to the treatments being studied. Environmental effects such as wind speed and direction are often inconsistent from the application of one treatment to another; therefore, variable environmental effects are superimposed upon the treatment effects. One approch for separating the environmental effects from the treatment effects is to apply a reference spray immediately following the treatment spray with different tracer materials added to the two sprays. The reference spray is applied in the same way each time; therefore, spray drift differences in the reference data reflect differences in environmental conditions. Treatment spray drift is affected by the treatment and the environment. The environmental effect can be adjusted out of the treatment data by using an analysis of covariance. The adjusted treatment means then reflect the treatment responses that would have occurred if the treatments had all been applied in the same environment. This allows statistical inferences to be made relative to the treatment effects, and this leads to a proper understanding of the relationships between the factors being studied and drift.

Technical Abstract: The evaluation of treatment effects on spray drift is difficult under field conditions. Factors that affect drift, such as wind speed and wind direction, cannot be controlled and are often inconsistent during drift studies. One approach for dealing with this problem is to apply a reference spray along with each treatment spray so that the reference experiences the same environmental effects as the treatment. The reference spray protocol is consistent throughout the experiment; therefore, relative differences in drift deposits from the reference spray are associated with changes in the environment. These data can be used in an analysis of covariance to adjust treatment means to compensate for differences in environmental conditions. The adjusted means reflect treatment responses that would have occurred if treatments had all been applied in the same environment. Sample collection and processing techniques are presented to enhance the quality and reduce handling. Details of the data analysis are illustrated that allow statistical inferences to be made relative to components of treatment structure.