Spatial Variation of Winegrape Yield and Berry Composition and their Relationships to Spatiotemporal Distribution of Soil Water Content

Spatiotemporal variability in vineyard soil water content (SWC) can affect yield and berry composition. The objectives of this study were to examine spatial variability in yield and berry composition over time and to quantify the contribution of spatial variability in SWC to these parameters. Yield, Brix, tannins, and total phenols were collected at the end of the berry ripening stage for 135 georeferenced points in 2012 and for 147 points in 2013 and 2014 in a Merlot vineyard in Gansu province, China. Volumetric SWC was measured multiple times at those points at different growth stages in each year. Spatial variation in yield showed moderate and similar spatial heterogeneity for different years, but the variation in berry composition was not consistent among years. Spatial variation in yield in 2012 and 2013 was best described by an exponential variogram model, but there was no spatial structure of yield in 2014. Low SWC at 0 to 20 cm depth corresponded to higher yield than did high SWC, and the opposite results were found for 40 to 60 cm. Spatiotemporal distribution of SWC explained more than 35% of total variation in yield and berry composition in the relatively dry year of 2012, but less than 10% in the relatively wet year of 2014. The contribution of spatiotemporal distributions of SWC to spatial variability in yield and berry composition varied according to field and weather conditions. This study provides a basis for developing site-specific management measures for better economic return.