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Title: Assessment of spray deposition with water-sensitive paper cards

item SALYANI, MASOUD - University Of Florida
item Zhu, Heping
item SWEEB, ROY - University Of Florida
item PAI, NARESH - University Of Florida

Submitted to: Agricultural Engineering International: CIGR Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2013
Publication Date: 11/26/2013
Publication URL:
Citation: Salyani, M., Zhu, H., Sweeb, R.D., Pai, N. 2013. Assessment of spray deposition with water-sensitive paper cards. Agricultural Engineering International: CIGR Journal. 15(2):101-111.

Interpretive Summary: Assessment of spray distribution usually involves the use of a quantitative method for determining spray deposition and drift. Water-sensitive papers have been used by spray researchers, farmers, and others to visualize or quantify spray distribution from ground and aerial applications. However, the use of WSP involves several practical limitations and needs special image analysis system with trained operator to convert spot size to droplet size. This study compared spray area coverage, droplet volume median diameter, and number of droplets obtained by using water sensitive papers with different image analysis systems, and established the relationship between droplet spot area coverage on water sensitive papers and spray deposition on absorbent paper targets. In general, the use of water sensitive papers may provide reasonably accurate area coverage estimation but may not be used to quantify the amount of spray deposits in most field applications. Therefore, the users must understand the problems and limitations associated with this technique before choosing it for a particular application.

Technical Abstract: Spatial distributions of spray droplets discharged from an airblast sprayer, were sampled on pairs of absorbent paper (AP) and water-sensitive paper (WSP) targets at several distances from the sprayer. Spray solutions, containing a fluorescent tracer, were discharged from two size nozzles to achieve low and high volume rates commonly used in citrus applications. Spray deposits on AP targets were measured by fluorometry and spray coverage areas on WSP cards were assessed by three independent image analysis systems. Generally, there were good correlations (R2 = 0.9085 to 0.9748) among the three imaging systems in measuring WSP percent area coverage. Lower volume rate (smaller droplets) provided more useful WSP targets than higher volume rate (larger droplets). Overall, there were somewhat weak correlations between WSP area coverage and AP spray deposition measurements. Volume median diameter and number of droplet stains on WSP cards , obtained by only two imaging systems, showed noticeable differences between the measurements of the two systems.