Abstract
<p style="text-align: justify;"><strong>Aim:</strong> The purpose of this study was to determine if multispectral high spatial resolution airborne imagery could be used to segregate zones in vineyards to target fruit of highest quality for premium winemaking. We hypothesized that remotely sensed data would correlate with vine size and leaf water potential (ψ), as well as with yield and berry composition.</p><p style="text-align: justify;"><strong>Methods and results:</strong> Hypotheses were tested in a 10-ha Riesling vineyard [Thirty Bench Winemakers, Beamsville (Ontario)]. The vineyard was delineated using GPS and 519 vines were geo-referenced. Six sub-blocks were delineated for study. Four were identified based on vine canopy size (low, high) with remote sensing in 2005. Airborne images were collected with a four-band digital camera every 3-4 weeks over 3 seasons (2007-2009). Normalized difference vegetation index (NDVI) values (NDVI-red, green) and greenness ratio were calculated from the images. Single-leaf reflectance spectra were collected to compare vegetation indices (VIs) obtained from ground-based and airborne remote-sensing data. Soil moisture, leaf ψ, yield components, vine size, and fruit composition were also measured. Strong positive correlations were observed between VIs and vine size throughout the growing season. Vines with higher VIs during average to dry years had enhanced fruit maturity (higher °Brix and lower titratable acidity). Berry monoterpenes always had the same relationship with remote sensing variables regardless of weather conditions.</p><p style="text-align: justify;"><strong>Conclusions:</strong> Remote sensing images can assist in delineating vineyard zones where fruit will be of different maturity levels, or will have different concentrations of aroma compounds. Those zones could be considered as sub-blocks and processed separately to make wines that reflect those terroir differences. Strongest relationships between remotely sensed VIs and berry composition variables occurred when images were taken around veraison.</p><strong>Significance and impact of the study:</strong> Remote sensing may be effective to quantify spatial variation in grape flavour potential within vineyards, in addition to characteristics such as water status, yield, and vine size. This study was unique by employing remote sensing in cover-cropped vineyards and using protocols for excluding spectral reflectance contributed by inter-row vegetation.
Highlights
Many studies have shown that fruit composition is impacted by vine vigour, whereby high vigour vines tend to compromise berry composition and quality (Bramley et al, 2011a-c; Hall et al, 2002; Johnson et al, 2003)
This study was unique by employing remote sensing in cover-cropped vineyards and using protocols for excluding spectral reflectance contributed by inter-row vegetation
For standard fruit maturity components, their relationship to airborne remote sensing was different depending on the weather conditions: in a normal to dry year, an increase of the vegetation indices (VIs) was associated with better technological fruit maturity
Summary
Many studies have shown that fruit composition is impacted by vine vigour, whereby high vigour vines tend to compromise berry composition and quality (Bramley et al, 2011a-c; Hall et al, 2002; Johnson et al, 2003). High vine vigour and high canopy density will negatively impact crop size the following growing season, by shading the forming buds and reducing fruitfulness (May et al, 1976; Sanchez and Dokoozlian, 2005). Others have shown that soil and vine water status both have a great effect on vine vigour, canopy development and fruit maturity (Hardie and Considine, 1976; Koundouras et al, 1999; Van Leeuwen, 2010; Van Leeuwen et al, 2003, 2004). The two principal methods are measurement of weight of cane prunings produced during the previous growing season (referred as vine size) and, the calculation of a leaf area index (Johnson et al, 2003)
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