Effect of emitter modifications on spray performance of a solid set canopy delivery system in a high-density apple orchard

Authors: RANJAN, RAKESH - Freshwater Institute; SINHA, RAJEEV - Washington State University; KHOT, LAV - Washington State University; HOHEISEL, GWEN-ALYN - Washington State University; GRIESHOP, MATTHEW - Michigan State University; LEDEBUHR, MARK - Application Insight, Llc

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2021
Publication Date: 11/30/2021
Citation: Ranjan, R., Sinha, R., Khot, L.R., Hoheisel, G., Grieshop, M.J., Ledebuhr, M. 2021. Effect of emitter modifications on spray performance of a solid set canopy delivery system in a high-density apple orchard. Sustainability. 13(23):13248. https://doi.org/10.3390/su132313248.
DOI: https://doi.org/10.3390/su132313248

Interpretive Summary: Solid Set Canopy Delivery Systems (SSCDS) are fixed agrochemical delivery systems composed of a network of in-canopy micro-emitters/nozzles for efficient and sustainable spray application in perennial crops. This study emphasizes the optimization of micro-emitters configured in shower down arrangement for uniform spray application with enhanced in-canopy spray deposition and coverage. Pertaining to this, two off-the-shelf micro-emitters were modified to have desirable spray attributes with a shorter wetted diameter and a canopy-confined spray pattern, improving within-canopy deposition and spray uniformity. The SSCDS treatments retrofitted with modified micro-emitters were observed to have numerically higher deposition and coverage compared to off-the-shelf micro-emitters. The emitter modification also resulted in relatively uniform spray distribution and coverage along the canopy zone and on both sides of the leaf. Overall, the SSCDS optimization significantly improved the spray performance of fixed spray delivery system.

Technical Abstract: Optimally configured solid set canopy delivery systems (SSCDS) can provide adequate spray performance in high-density apple orchards with a minimized risk of off-target pesticide drift. SSCDS configured in a shower-down emitter arrangement have been reported to be the simplest and most economical system. However, existing off-the-shelf emitters used in shower-down configurations have resulted in minimal deposition in lower canopy zones. Therefore, this study was focused on the modifications of off-the-shelf emitters to obtain a desirable spray pattern for adequate spray deposition in all the canopy zones. The modifications include redesigning the impact plate of two existing micro-emitters. Field tests were conducted to evaluate the spray performance of SSCDS with the non-modified emitters (treatment: SD1 and SD3) and contrast the results with modified emitters (treatment: SD2 and SD4). While the treatments SD1 and SD3 had off-the-shelf emitters with swivel plate and static spreader, respectively, the treatment SD2 and SD4 had similar emitters with modified impactor plates. In each treatment block, the apple canopy was divided into six zones and sprayed with a 500 ppm fluorescent tracer solution. Mylar cards and water-sensitive paper samplers were placed on the adaxial and abaxial leaf surfaces in each canopy zone to quantify spray deposition and coverage, respectively. The SSCDS treatments retrofitted with modified emitters, i.e., SD2 and SD4, were observed to have uniform and numerically higher deposition and coverage compared to SD1 and SD3. The SSCDS treatment with modified static spreader (i.e., SD4) resulted in the highest overall spray deposition (1405.7 ± 156.4 ng cm-2 [mean ± standard error]) with improved mid (1121.6 ± 186.9 ng cm-2) and bottom (895.6 ±149.3 ng cm-2) canopy deposition. Overall, the proposed emitter modification assisted in improved SSCDS spray performances and may be a way forward toward large-scale emplacements of such systems.