Characterization of In-Swath Spray Deposition for CP-11TT Flat-Fan Nozzles Used in Low-Volume Aerial Application of Crop Production and Protection Materials

A study was conducted to quantify spray deposit characteristics of the low-drift CP flat-fan nozzle. In the study, CP flat-fan nozzles with selectable tips and swivel angles were evaluated for droplet spectra and coverage using water-sensitive paper (WSP) placed in the spray swath. Three nozzle angles (23, 38, and 53 downward from the horizontal) and three application volumes (9.5, 19, and 28.5 L ha-1) were coupled with appropriate flat-fan tips as required by the target application volume. Droplet spectra of the WSP over the spray swath were calculated to produce DV0.1, DV0.5 (also referred as volume median diameter or VMD), and DV0.9. Statistical results showed that higher nozzle spray flow rates resulted in higher percentage spray coverage and that relative humidity at the time of spraying had a significant positive effect on spray coverage (p = 0.0007). Average VMD did not differ much between the 38 and 53 downward angles, but average VMD for the 23 angle was 50% higher and more variable than for the 38 and 53 angles across flow rates. Relative span, which is an indication of droplet size ranges, was lower in the field trials than the values indicated by the USDA models at low flow rates. Baseline data obtained in the swath on droplet characteristics can help aerial applicators verify the correct spray tip for a given flow rate and nozzle angle for a desired droplet spectrum and sufficient spray coverage.