Unmanned aerial sprayers: evaluating platform configurations and flight patterns for effective chemical applications in modern vineyards

Unmanned Aerial Sprayers (UASs) are being sought after as a possible alternative to knapsack sprayers in topographically challenging vineyards. However, prior work has identified that UASs have issues with delivering adequate spray mix to the bottom canopy zones. This study was thus conducted to understand and potentially improve spray delivery to the grapevine bottom canopy zones through two flight patterns (cross-row and row-aligned) and three commercial UASs platform configurations (AGRAS T20, AGRAS T30, and AGRAS T30 ‘orchard configuration’, DJI Technology Co.). Three flights were conducted for each treatment at an application rate of 109 L ha-1 (11.47 GPA) over independent replicate test blocks. All tests were conducted in a vertical shoot position (VSP) trained vineyard (cv. Chardonnay). Water sensitive papers and mylar cards were used to quantify coverage (%) and deposition (ng cm-2), respectively. Overall, cross-row flight applications (coverage: 6.70 ± 1.38 % [mean ± standard error], deposition: 104.54 ± 17.71 ng cm-2) failed to provide significantly different (p > 0.05) spray delivery as compared to the row-aligned operations (coverage: 10.10 ± 2.14 %, deposition: 83.81 ± 11.17 ng cm-2). Similarly, coverage and deposition data collected for the three UAS geometries failed to present significant differences (p > 0.05). Regardless of configuration or flight pattern, the bottom canopy zone received significantly lower deposition than the top canopy zone across treatments. Further engineering towards optimization of UAS geometry is needed for efficient chemical application in modern VSP trained vineyards.