Integrative Effects of Vine Water Relations and Grape Ripeness Level of Vitis vinifera L. cv. Shiraz/Richter 99. I. Physiological Changes and Vegetative-Reproductive Growth Balances

The water relations and physiological status of the grapevine are critical for obtaining a quality product andfor fully exploring vineyard and grape potential. The objective of this investigation was to determine theeffect of grapevine water status (induced by means of two field water capacity-based irrigation levels, 75%and 100%, applied at single and combined vine developmental stages) on morphological and physiologicalchanges in Vitis vinifera L. cv. Shiraz/Richter 99 grapevines and grapes (harvested at different solublesolid levels) under field conditions. The integrative effects of vine water relations and grape ripeness level,specifically in a Mediterranean high winter rainfall area, have not yet been investigated systematically. Theterroir affected the reaction of the vines to treatments. The soil displayed high water-holding capacity anda buffer against favourable evapotranspiration conditions, even with a western aspect and being subjectedto long and relatively dry seasons, with frequent occurrence of high temperatures and grapevines withfully developed canopies. The vines did not seem overly stressed – in line with the relatively high basesoil water fractions of mostly more than 50% of field water capacity. Primary and secondary leaf waterpotential and stem water potential displayed similar patterns and the water potential of the primary andsecondary leaves was similar. Despite relatively high base soil water contents that prevented excessivelylow plant water potential and classic leaf and berry behaviour to surface, the vines still responded in anoticeable way to volume and timing of irrigation in relation to the grape ripeness level status. Waterrelations, ripeness level and terroir conditions showed an integrated, steering impact on physiological,vegetative and reproductive behaviour. Post-véraison irrigated vines were expected to maintain relativelyhigh water potential during the last weeks of the ripening period, but this seemed not to be the case. Allvines seemed to have recuperated/stabilised during this time, maintaining their water balances. Physical,physiological and compositional changes in the berry during late ripening under field conditions wereclarified further. New information was obtained on the relationships between the behaviour of the rootsystem, canopy and grapes and the changing terroir conditions during the ripening period

Integrative Effects of Vine Water Relations and Grape Ripeness Level of Vitis vinifera L. cv. Shiraz/Richter 99. II. Grape Composition and Wine Quality

Regulation of grapevine water status is a common practice to manipulate grape composition and winequality. In this investigation the effect of plant water status (two field water capacity-based irrigation levels,75% and 100%, applied at single and combined vine developmental stages) and ripeness level (harvestingat different soluble solid levels) on grape composition and wine quality of Vitis vinifera L. cv. Shiraz/Richter 99 was determined. Integrative effects of vine water relations and grape ripeness level, specificallyin a Mediterranean high winter rainfall area, have not yet been investigated systematically. Source:sinkmechanisms and dynamics and compositional and physical changes during both green berry and ripeningperiods (and in response to environment changes), seemed critical for the final grape composition and winequality/style. Despite relatively favourable conditions of the experiment terroir, additional water was stillrequired to obtain best grape and wine quality. Skin colour and total phenolic contents were stimulated inparticular by 75% (field water capacity) pea size (PS) irrigation, post-véraison (PV) irrigation and 75% peasize+post-véraison irrigation, until the last harvest stage. Treatments that included post-véraison irrigationwere not negative in terms of ripening parameters. Increasing total soluble solids with ripening were notfollowed in parallel by anthocyanin potential. Anthocyanin extractability increased with ripening. A late,overripe harvest may result in wines that are slightly better coloured, but highly alcoholic and tannic.Furthermore, at high ripeness level, differences between treatments largely diminished. Over-ripenessof grapes may have tempering and even negative effects on expected outcomes of seasonal cultivationefforts to produce unique wines. This would not favour economic viability. Although non-irrigated winesfailed to result in exceptional wine quality at any harvest stage, a better result in overall quality wasobtained in comparison to irrigation treatments applied at all stages. Berry and wine composition resultscorresponded with findings on wine sensorial quality. The 75% PS, PV irrigation, and 75% PS+PVirrigation consistently resulted in good quality wines. At the first harvest stage, 75% PV, 100% PV, 75%PS+V and 75% PS+PV irrigations gave most prominent wines; at the second harvest stage, vines irrigated75% at PS, 75% at PS+PV and 75% at PV delivered most prominent wines; and at the third harveststage, 75% PV, 100% PV, 75% PS and 75% PS+PV resulted in most prominent wines. These treatmentsrepresented different wine styles at each harvest stage. Restricted PS irrigation and PV irrigation, as singleor combined treatments, featured prominently in favouring grape and wine composition and wine sensorialquality. Physical and compositional changes in ripening berries and the impact on wine quality and stylewere further clarified. New perspectives on managing time of harvesting with varying vine water status aregiven. Recommendations on vine water status management strategies required to obtain different grapecomposition and wine style are made

Effect of Trellis Conversion on the Performance of Chenin blanc/ 99 Richter Grapevines

To accommodate the excessive vegetative growth of a 9-year old, 3.0 m x 1.2 m spaced and vertically trellised Chenin bland99 Richter vineyard, vines were converted to double the original cordon length by removing alternate vines or by extending the cordon laterally in a horizontal plane as per Lyre trellising system. By extending the cordon, shoot vigour was reduced, resulting in an improvement in canopy appearance and microclimate, particularly in the case of the latter system (higher canopy:root volume ratio). Yield increased by 11 % and 65% for the vertically trellised vines with extended cordon length and those on the Lyre system, respectively.  Grape composition was not affected, whereas the severity of Botrytis infection tended to decrease. Wine typicity was enhanced by trellis conversion. Labour input in terms of pruning, harvesting and seasonal canopy management was lower for the vertically trellised vines with extended cordon length, but higher for the vines on the Lyre system; the additional yield, however, still resulted in respectively 15 % and 69 % higher total income. The results showed that the "original" vigour (growth capacity) was better accommodated and distributed by extending cordon length, particularly for the Lyre system, thereby resulting in higher yields of at least similar grape and wine quality and higher income than before conversion

Effect of Seasonal Canopy Management on the Performance of Chenin blanc/99 Richter Grapevines

The effect of seasonal canopy management on the performance of a Chenin blanc/99Richter vineyard with excessive vegetative growth and trained onto a Lengthened Perold trellising system, was studied. No canopy management (shoots growing in all directions) resulted in over-exposure of the bunch zone directly above the cordon, whereas sunlight reflection from the soil was drastically reduced. In contrast, canopy management led to a much more balanced penetration of sunlight into the bunch zone - here, shoot positioning played a big role. Air flow through the canopy was highest when partial defoliation, in combination with suckering and shoot positioning, was applied; these practices had the highest impact on canopy microclimate and appearance. Canopy management reduced the incidence and severity of Botrytis/sour rot - shoot positioning in particular seemed critical. Highest yields were obtained by applying shoot positioning and defoliation or topping. Although suckering was labour intensive and reduced yields, it resulted in significant labour savings for critical time-dependent actions such as pruning and harvesting. Total grape quality and wine typical flavour were improved by seasonal canopy management

Effect of Altered Canopy:Root Volume Ratio on Grapevine Growth Compensation

Nine-year-old, intensively irrigated, 3.0 x 1.2 m spaced and vertically trellised (5-strand) Chenin blanc/99 Richter vines were converted to double the original cordon length by either removing alternate vines or by implementing a Lyre trellising system. In the former case the root volume was doubled, whereas in the latter case it was kept the same as for the non-converted vines. After five years, a root profile study showed that roots of the single-cordoned, vertically trellised vines with extended cordon were distributed beyond the original soil volume (before conversion); this was not the case for the Lyre system. No difference in root density occurred between vines of converted systems.  The available soil volume was apparently better colonised by roots of the converted systems, mainly because of an increase in fine roots. The greatest reduction in individual shoot growth was found for vines trained to the Lyre system. Yield per vine varied according to cane mass. Yield per hectare of vines trained to the vertical trellis with extended cordon space and the Lyre system increased significantly. Yield:cane mass ratios of 11, 15 and 16 were found in the case of the vertical, the vertical with extended cordons and the Lyre systems, respectively. The results indicated that shoot growth was better accommodated and distributed by extending cordon length, particularly when the ratio of cordon length to root volume was increased (as for the Lyre system). Compensatory growth occurred when both above-ground and subterranean growth volumes were increased. Preventing compensatory growth by the root system, resulted in balanced growth and improved microclimatic conditions for pest and disease control and grape ripening.  This principle may be implemented as a long-term solution to problems associated with excessive vigour

PVGIS: a free online solar photovoltaic calculator tool to optimise light harvesting in viticulture

The Photovoltaic Geographical Information System (PVGIS ©European Communities, 2001–2017) had been developed from solar radiation data estimated from satellite using the Satellite Application Facility on Climate Monitoring (CM SAF) models, representing the period 1996-2011. In areas North of 58º N the data are derived from ground station measurements collected within the European Solar Radiation Atlas and interpolated spatially. The PVGIS service allows to simulate the photovoltaic potential of a PV system, according to the site location and horizon mask, the PV technology, installed pick power, yield and energy losses, as well as mounting options like slope (0=horizontal 90=vertical) and azimuth (-90=oriented to the East, 0= to the South, 90 to the West, + or -180 to the North). Several web-tools available from the PVGIS online service can be used in viticulture. In particular, the “Show horizon” option allows the calculation of the topographic (as affected by the surrounding hills and mountains) sunrise, sunset, and maximum potential day length, on a sunny day with no cloud cover. Moreover, the “Daily radiation” tool offers the possibility to calculate the monthly irradiance on the PV surface. Therefore, the PVGIS service can be used to simulate the monthly irradiance on the canopy surface using slope=90 (vertical) and the row orientation angle as azimuth value. Finally, the “PV Estimation” service provides the estimation of the optimum inclination and orientation of the PV module (i.e. canopy) as affected by the horizon mask, to maximize the annual light interception. PVGIS services and queries can also be embedded into new tools (both local and online) to support the site selection and a proper vineyard design (row direction, row and vine spacing, trellis system, etc.)

Starch Concentrations in Grapevine Leaves, Berries and Roots and the Effect of Canopy Management

Diurnal and seasonal starch changes in leaves, berries and roots of Vitis vinifera L. cv. Cabernet Sauvignon/99 Richter and the effect of canopy management (a combination of suckering, shoot positioning, and 33% defoliation) on these processes were investigated under field conditions. An increase in starch concentration of basal leaves occurred from the morning to the afternoon during the most active vegetative growth period (up to veraison), indicating a proportional change in storage or export of assimilates between day and night. During later developmental stages diurnal starch levels slightly declined or remained the same. Seasonally, leaf starch remained relatively stable until veraison, whereafter it increased, reaching highest concentrations at the post-harvest stage. Canopy management generally increased leaf starch concentrations. Berries contained no significant amounts of starch.  Root starch concentrations were usually higher than those of leaves. Diurnally as well as seasonally, root starch accumulation patterns coincided with those of leaves, indicating a close relationship between source and sink tissue. Canopy management resulted in stable diurnal root starch concentrations without affecting the daily mean starch level; afternoon values of treated vines were, however, generally lower. The results imply that carbohydrate supply and starch-synthesising enzyme systems were not limited by manipulating the canopy and decreasing foliage. It seems, however, that particularly late in the season starch accumulation in roots may be delayed by canopy manipulation as applied. This indicates a shift in sucrose partitioning and its utilisation in roots and other sink areas, e.g. the berries, when the canopy is manipulated

Linking grapevine row orientation to a changing climate in South Africa

International audienc

Composition of Sauvignon blanc Grapes as Affected by Pre-veraison Canopy Manipulation and Ripeness Level

The implications of pre-veraison canopy management and ripeness level (19°B and 21°B) on microclimate and grape and must composition were determined on intensively micro-sprinkler irrigated Vitis vinifera L. cv. Sauvignon blanc/110 Richter vines, grown on a vertical trellis in the Breede River Valley of South Africa. Rows were east-west orientated and vines spaced 2.75 m x 1.5 m. Spurs were spaced approximately 15 cm apart. Canopy management consisted of different combinations of seasonal practices (suckering, shoot positioning, topping, leaf thinning) during the pre-veraison growth period (just after budding to pea size berry) in order to accommodate foliage and to improve the canopy microclimate. Treatments that included leaf thinning improved the light conditions in the canopy without a noticeable effect on other microclimate parameters as well as bunch and berry sap temperature. The must pH remained relatively stable, with an increase in ripeness level from 19°B to 21°B, whereas the rest of the measured grape composition components followed a decreasing pattern during this period.  Treatments that included leaf thinning tended to increase titratable acidity and decrease pH at both ripeness levels.  Additional leaf thinning (up to the lower half of the canopy at pea size) increased the glucose and fructose concentrations without changing their ratio. It also decreased the malic acid concentrations of the berries, whereas the free-amino-nitrogen content of the must was stimulated.  Furthermore, leaf thinning in general increased the monoterpene content (fruity aroma) and apparently enhanced the 2-methoxy-3-isobutylpyrazine content (grassy/green pepper aroma), thereby increasing the total measured aroma profile. Both palate and flavour profiles were therefore changed by applying pre-veraison seasonal canopy management. The data emphasised the importance of the correct timing and application of canopy management. This seemed to be of great significance in the realisation of an improved grape composition, even for S. blanc subjected to a relatively hot terroir

Integrating geographic information systems and hemispherical photography in the assessment of canopy light profiles in a vineyard

The light conditions in a vineyard primarily depend on the latitude of the vineyard and day of the year. Based on these parameters, the exact daily Sun path can be calculated with astronomical functions. However, effective Sun hours also depend on the topography of the territory, both for direct and diffuse radiation, as a result of the presence of hills and mountains on the Sun path (direct radiation) or, in general, reducing the sky fraction (diffuse radiation). A 360° orographic profile can be assessed by topographic survey, by using hemispherical pictures or Geographic Information Systems (GIS) and Digital Elevation Models (DEM). Moreover, row orientation, vine spacing, trellis system and height, leaf area density, exposure side, etc. further affect the light micro-climate within the canopy and, particularly, at bunch level, which may have consequences for the temperature and composition of the berries. In the present work two grapevine row orientations (NS and EW) were used to integrate various tools (Photovoltaic Geographical Information System, Visual Basic functions for the calculation of solar position and radiation, and results from the processing of hemispherical pictures) into an Excel Worksheet, called “SunMask”, that can be used as a new multi-purpose tool to 1) quickly calculate both the astronomic and the topographic sunrise, sunset, and maximum potential day length, 2) evaluate the effect of row orientation and canopy dimensions on the transmittance of the direct solar beam at high temporal resolution and, finally, 3) separate the effect of topographic and canopy masks on the Sun hours under clear-sky conditions. By combining the different tools in SunMask, both the astronomic and topographic (as affected by the surrounding hills and mountains) sunrise, sunset, and maximum potential day length can be quickly and easily calculated for every specific vineyard terroir/location at any date or time in Europe, Africa and Asia. In addition, the software allows the evaluation of the effect of the canopy mask on the transmittance of the direct solar beam. SunMask will be a very important asset to improve information regarding radiation profiles of vineyards at meso- and micro-levels. It will be most valuable in the assessment of terroir suitability for vineyard establishment as well as for viticulture practice choices and the management of grapevine canopies