Effect of Partial Rootzone Drying on Vine Water Relation, Vegetative Growth

Partial rootzone drying (PRD), derived from split root research, is an irrigation technique which modifies vine growth and development by keeping part of the rootzone dry and the rest of the rootzone well watered. The objective of this research was to investigate the feasibility and effect of PRD on vine water relation, vegetative growth, mineral nutrition, yield components, fruit composition, wine chemistry, and wine sensory characteristics in mature Sauvignon Blanc grapevines (Vitis vinifera L.) grown in the San Joaquin Valley of California, in comparison with conventional drip irrigation (CDI). Vineyard water use and canopy microclimate were also evaluated. This study was conducted in a 15-acre bilateral cordon trained mature Sauvignon Blanc/Freedom vineyard on Hanford Sandy Loam in the California State University, Fresno Agricultural Laboratory. Treatment factors included PRD and CDI at 0.4 or 0.8 evapotranspiration, resulting in 4 treatments, CDI-0.4, CDI-0.8, PRD-0.4, and PRD-0.8. Partial stomatal closure due to PRD resulted in a decrease in stomatal conductance (g), transpiration rate (E), and vine vegetative growth, and in turn, an improvement in water use efficiency. Yield, fruit composition and wine chemistry were not significantly affected by PRD treatment nor by the amount of water applied. Two years field experiments demonstrated that PRD offers a way for producing a vine with a better balance between vegetative and reproductive development, reducing vine water use, controlling vine vigor and canopy density, while maintaining crop yields when compared to standard vineyard irrigation practices. PRD holds potential to be a useful management practice for high vigor vineyards in the San Joaquin Valley of California. However, it seemed that most of the observed PRD effect on vine performance and vine physiology was resulted from the reduction of irrigation water rather than switching the wetting and drying sides. Further research is needed to investigate the necessity of alternating the sides of wetting and drying, because PRD consists of reduced amount of irrigation water and the switching.