Spatial variability in Ontario Riesling vineyards: I. Soil, vine water status and vine performance

Abstract

Aim: The major focus of this research was to explain the so-called terroir effects that impact grapevine yield components, berry composition, and wine varietal character. To elucidate potential contributors to the terroir effect, vine water status [midday leaf water potential (ψ)] was chosen as a major determinant. The hypothesis of this component of the study was that consistent leaf ψ zones could be identified within vineyard sites and that vine water status would play a major role in vine performance and yield components. Soil texture was anticipated to play a role indirectly through its water-holding capacity.Methods and materials: To test this hypothesis, ten Riesling vineyards representative of each Vintners Quality Alliance of Ontario sub-appellation were selected within the Niagara Peninsula. These vineyards were delineated using global positioning systems and 75–80 sentinel vines were geo-referenced within a sampling grid for data collection. During the 2005–2007 growing seasons, leaf ψ measurements were collected bi-weekly from a subset of these sentinel vines. Data were collected on soil texture and composition, soil water content (SWC), vine performance and yield components. These variables were mapped using geographical information systems software and relationships between them were elucidated.Results: Vineyards were variable in terms of soil texture, composition, nutrition, and moisture. However, in general, few consistent relationships with soil composition variables were found. As hypothesized, consistent leaf ψ zones were identified within vineyards in all three vintages. Some geospatial patterns and relationships were spatially and temporally stable within vineyards. In many cases, spatial distribution of leaf ψ was temporally stable within vineyards despite different weather conditions during each growing season. Spatial trends within vineyards for SWC and leaf ψ were temporally stable over the 3-year period for eight vineyards. Generally, spatial relationships between leaf ψ, SWC, vine size, berry weight and yield were also temporally stable. Some inconsistencies in spatial distribution of variables were attributable to winter injury.Conclusions: Many viticultural variables such as leaf ψ, vine size, berry weight, and yield were spatially variable and, as hypothesized, consistent leaf ψ zones were identified within vineyards in three distinct vintages. Many geospatial patterns and relationships were determined and were temporally stable, and this temporal stability in these variables occurred despite different growing seasons. The strongest relationships were those concerning leaf ψ, SWC, vine size, and berry weight. No consistent relationships were found concerning soil composition. The most consistent soil variables that impacted vine performance and yield components were physical properties, particularly texture.Significance and impact of the study: Soil had some indirect effects, but leaf ψ was more likely a major contributor to the terroir effect, as it had a major impact on vine size, berry weight and yield in many vineyards across multiple vintages. Temporal stability is required for many practical geomatic applications to be initiated in vineyards, but it is also of importance to future research endeavors for this project as well as others.

Spatial variability in Ontario Riesling vineyards. II. Berry composition

“…At the GLK site, consistent zones of leaf ψ and SWC were found in 2005-2007 despite different weather conditions (Willwerth and Reynolds 2020). Maps for four sites (GLK, CDC, MYR, and CSC) are included in the main body of the paper (Figs.…”

“…The SWC (%) and leaf ψ measurements were taken biweekly in each vineyard (every 10-14 d) from sentinel vines between the end of June and early September (beginning of fruit set to preharvest) as described in Willwerth and Reynolds (2020). Soil analyses, including pH, organic matter (OM) concentration, elemental concentration, cation-exchange capacity (CEC), and base saturation (BS), were performed on one soil sample collected from every fourth sentinel vine (Willwerth and Reynolds 2020). For each sentinel vine, data were collected annually at vine dormancy for weight of cane prunings as an estimate of vine vigor (vine size).…”

“…All results shown are from the 2005-2007 growing seasons. As in Willwerth and Reynolds (2020), three sites were omitted from this paper due to significant winter injury in the 2004-2005 winter that substantially decreased yields (Lambert, Reif, and Vailmont), and powdery mildew in 2006 (Vailmont). Meteorological data depicting temperature and rainfall events for each growing season are depicted in Supplementary Fig.…”

“…Results are subdivided into tables depicting linear correlations for each vineyard, geospatial maps depicting spatial variability in fruit composition variables for each site, and PCA results and interpretations. References to the companion manuscript (Willwerth and Reynolds 2020) are given for correlative relationships between leaf ψ and yield components.…”

“…It was hypothesized that consistent leaf ψ zones would be identified within vineyard blocks and that vine water status would play a major role in fruit composition while soil type would determine water-holding capacity and water supply to the vine. Data on soil texture and composition, SWC, leaf ψ, and yield components are included in a companion manuscript (Willwerth and Reynolds 2020). Data describing sensory differences between wines from high and low water status zones in these vineyards are found in Willwerth et al (2018).…”