Geraldine Diverres* and Markus Keller
*Washington State University, 24106 N Bunn Road, Prosser, WA 99350 (r.diverresnaranjo@wsu.edu)

Inadequate irrigation management can limit vineyard productivity and fruit quality, diminishing potential revenues and resource-use efficiency. Regulated deficit irrigation (RDI) and partial rootzone drying (PRD) were compared to non-stress irrigation (FULL) in a Riesling vineyard in the Yakima Valley. This project’s objective was to determine the usefulness and sustainability of each technique for high-quality white winegrape production in eastern Washington. The results show that canopy growth, canopy architecture, and final yield were significantly affected by the irrigation strategy. RDI vines had smaller canopies with greater sun exposure in the fruiting zone and their harvest yield was lower than those of PRD and FULL vines. On the other hand, PRD vines had denser canopies, less-exposed clusters, and did not show differences in yield compared to FULL. No differences were found between any treatments in terms of fruit composition at harvest (total soluble solids, pH, and titratable acidity). Given these results, PRD may allow considerable reduction in water use for white winegrape production without affecting yield and quality in arid climates like eastern Washington.

Funding Support: NSF/USDA Cyber Physical Systems Program and the Washington State Grape and Wine Research Program