Effect of Partial Rootzone Drying on Vine Water Relation, Vegetative Growth, Mineral Nutrition, Yield Components, Fruit Composition, and Wine Quality in Sauvignon Blanc Grapevines
Partial rootzone drying (PRD) is an irrigation technique designed to keep part of the rootzone dry and the rest of the rootzone well-watered, in comparison with conventional drip irrigation (CDI) with the entire rootzone irrigated. 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. 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 irrigation method (PRD and CDI) and irrigation rate (0.4 or 0.8 evapotranspiration, ETc), resulting in 4 treatments, CDI-0.4, CDI-0.8, PRD-0.4, and PRD-0.8. Partial stomatal closure due to reduced irrigation rate 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 either irrigation method or irrigation rate. Three years? field experiments demonstrated that reducing irrigation rate 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 yield when compared to standard vineyard irrigation practices. Most of the observed PRD-0.4 effect on vine performance and vine physiology was the result of the reduced irrigation rate rather than keeping part of the rootzone dry and the rest of the rootzone well watered.
