Vine Vigor Research Articles

Traditional and innovative summer pruning techniques for vineyard management

This review paper highlights physiological and vine performance effects of widely adopted summer pruning operations such as leaf removal, shoot trimming and positioning and cluster thinning. Leaf removal is addressed either under its traditional configuration, i.e. removing in dense canopies some or all leaves around clusters usually pre-veraison to improve fruit microclimate and facilitate spraying and early (pre-flowering) defoliation primarily aimed at inducing looser clusters via a concurrent reduction of fruit-set and berry size. Time consuming and still non mechanisable cluster thinning is evaluated primarily in terms of response variability vs. season and intensity with emphasis on lack of significant reduction of final yield per vine in thinned treatments when large crop compensation occurs. Variability of expected final grape composition improvements in thinned vines is also discussed based on the actual vine balance when the operation is performed. Although fully mechanisable, shoot trimming is still a debated choice in terms of timing and severity. While severe (i.e. fewer than six or seven main leaves retained) and late (i.e. several weeks after bloom) cuts should possibly be avoided, the effects of shoot trimming on final grape composition is discussed as a function of seasonal changes in leaf area development, demography, fraction of lateral leaves from the total and leaf to fruit ratio. It is indicated that, for vertically shoot-positioned trellises, if the support trellising is correctly designed and vine vigour is balanced, timing and severity of trimming are dictated by the vine “itself” rather than by grower choices. Overall, this review underscores the importance of leading the vineyard to a “natural” control of vegetative growth, which would minimise the need for an extensive use of summer pruning. In other words, such vineyard operations should be viewed not just as something the growers “have to do”, instead as specific tools used to achieve targeted final grape composition.

Researches on the Varieties Behavior that Are Part of the Feteasc? Group Sort, in Different Climatic Conditions in Western Part of Country

Researches aimed the most known, widespread and valuable indigenous varieties cultivated in three different areas in the western part of Romania: Buzias, Minis and Recas. These were analyzed and compared with the varieties Italian Riesling and Cabernet Sauvignon from the point of view of vine vigor and the quantity and quality of grapes. Indigenous varieties through product quality achieved constitute a valuable source for obtaining of typical and authentic wines, able to satisfy consumers becoming increasingly advised and pretentious, wishing to consume quality wine specific of areas of origin. Harvests were superior compared with the control at varieties for white wines Feteasca alba and Feteasca regala in all three areas studied, except the Feteasca neagra variety, which compared with Cabernet Sauvignon gave slightly inferior productions at Minis and Recas but registered higher sugar accumulations in all areas of research. (Dobrei et al., 2009). Romania was in ancient times and is a country with tradition in the culture of vines, which had in every winegrowing area a valuable traditional assortment. After the massive introduction of universal varieties in culture, indigenous varieties have been passed temporarily into a secondary position, although it presents ampelographic and special technological attributes (Dobrei et al., 2008; Dobrei et al., 2005). The research was conducted during 2010 in three prestigious wine-growing areas in the western part of Romania (Minis – Maderat, Recas and Buzias) and targeted varieties Feteasca Regala, Feteasca Neagra and Feteasca Alba were analyzed compared with the varieties Italian Riesling and Cabernet Sauvignon considered witnesses. The vineyards in which were done the researches are in full maturity period, planting distances between rows are 2.2 m and 1 m spacing between the vines, cutting types are Guyot on the trunk and cordon Lenz Moser. Observations and measurements were made on annual matured increases, leaves area, the quantity and quality of production obtained. Results were analyzed and statistically interpreted using the method of calculating analysis of variance.

An Investigation of Training System, Pruning Severity, Spur Length, and Shoot Positioning on Cynthiana/Norton Grapes

This five-year study evaluated the effects of Geneva double-curtain (GDC) and single-curtain (SC) training systems, 30+10 and 60+10 balanced pruning severities, 3- and 6-node spur lengths, and shoot positioning on yield and fruit composition of Arkansas-grown Cynthiana/Norton, <i>aestivalis-</i>type grapes. The GDC-trained vines had a 46% higher yield than SC-trained vines, but yield per m/cordon was lower for GDC-trained vines. Additional yield on GDC-trained vines appeared to come from noncount shoots. Vine dormant prunings, number of retained nodes, and cluster weights were similar between training systems. Juice pH was lower on GDC-trained vines; other measures of fruit composition were similar between training systems. Pruning to a 60+10 severity increased the number of retained nodes and increased yield and clusters per vine as compared to 30+10 but did not affect fruit composition. There was no difference in yield on vines pruned to 3- or 6-node spurs and there was no difference in fruitfulness associated with node position along the spur. Pruning to 3-node spurs increased the percentage of soluble solids while maintaining slightly greater vine vigor than pruning to 6-node spurs. Shoot positioning did not affect vine yield but did reduce vine vigor and lower fruit pH. Shoot positioning should be considered based on individual vineyard vigor and production methods.

Role of Summer Dormant Perennial Grasses as Intercrops in Rainfed Mediterranean Vineyards

ABSTRACTGrass swards are increasingly used in vineyards to improve ecosystem function, reduce vine vigor, and enhance grape (Vitis vinifera L.) quality. In Mediterranean rainfed vineyards, the use of intercropping has been constrained because of excessive competition for water with the vine over summer. We aimed to test cultivars of Mediterranean forage grasses with a range of summer dormancy, which confers low competitiveness for water and high persistence. A 4‐yr experiment compared a bare soil control and three perennial grass cultivars as interrows in a vineyard: orchardgrass (Dactylis glomerata L.) ‘Kasbah’ and ‘Bacchus’ and tall fescue [Lolium arundinaceum (Schreb.) Darbysh] ‘Centurion’. In the spring of 2006, Centurion had extracted water to the 150‐cm depth, whereas neither orchardgrasses had extracted water beyond the 120‐cm depth. In the summers of 2006 and 2007, Centurion used 30 to 50 mm more of the soil water reserve in the 0‐ to 150‐cm soil layer than the bare soil control. Vine predawn leaf water potential, vine leaf area index (LAI), and biomass of pruned shoot and of vine fruit were also significantly affected by intercrops. The best intercrop was the least competitive cultivar, Kasbah, because of its low biomass production and complete summer dormancy. Bacchus is not summer dormant and was the least persistent. Centurion was the most competitive because of its deep root system and incomplete summer dormancy. The results raise the needs for breeding a larger range of adapted cultivars for intercropping rainfed Mediterranean vineyards.

Commercial Digital Camera to Estimate Postharvest Leaf Area Index in Vitis vinifera L. cv. Cabernet Sauvignon on a Vertical Trellis

The leaf area index (LAI) of a vineyard (Vitis vinifera L.) cv. Cabernet Sauvignon located in the commune of Cauquenes, Maule Region in Chile, was estimated from digital images obtained with a commercial camera using two indirect methods: Leaf Area Gap and Brightness (LAGB) and Photogrammetric Leaf Area Quantification System (PLAQS). The latter requires deleafing of the grapevine. In a normalized difference vegetation index (NDVI) map, three points of vine vigor were selected: high, medium, and low for which horizontal and vertical images were obtained. Images were filtered with the Arc View GIS 3.1 program to provide only leaf images and corresponding pixel numbers. Image area and square meters per linear meter were calculated. The best models were selected from three linear regression adjustments: i) LAI of LAGB vertical images of with LAI of PLAQS, ii) LAI of PLAQS horizontal images with and, iii) LAI of both types of images with PLAQS. The parameters in all models were significant. Adjustment between the LAGB and PLAQS vertical images provides greater simplicity and easy calculation since it requires only a vertical image to estimate LAI. Images thus obtained can accurately estimate LAI in this type of cultivar.

Vine vigour effects on leaf gas exchange and resource utilisation

Background and Aims: Variability in vine vigour is a commonly observed feature in vineyard blocks. Although this aspect is well recognised among viticulturalists, impacts of vigour variability on vine function and resource use efficiency are seldom considered in management decision-making. This study examined influences of vine vigour variability on vine physiological performance and resource use in a commercially managed vineyard block. Methods and Results: The vineyard block was divided into different vigour zones using plant cell density data derived from aerial multi-spectral imaging of the study block. Gas exchange and under-vine soil moisture status were measured in some of the vigour zones. Low vigour vines had consistently lower photosynthesis and stomatal conductance rates than high vigour vines. The differences were evident both during soil-drying and rewetting. Similarly, irrigation water utilisation was markedly lower in low than in high vigour vines. Vine fruit yield was linearly and positively related to vines' capacity to utilise applied water. Conclusions: Vigour has considerable influence on vine physiological performance and on resource utilisation capacity. Uniform irrigation application to a block with variable vigour (which is the norm currently) leads to spatially inefficient resource use, and consequently to a marked within-block variation in irrigation water productivity. Significance of the Study: The demonstration that variation in vigour has a corresponding effect on resource utilisation has direct relevance for managing vineyard inputs such as irrigation or fertilisers.

The Relationship between Grapevine Vigour and N-Mineralization of Soil from Selected Cool Climate Vineyards in Victoria, Australia

Excess vigour is a problem in cool climate vineyards in Australia due to high soil N-fertility. High and low vigour blocks in three cool climate vineyards in Victoria, Australia, was surveyed. The relationship between soil N-fertility and grapevine vigour was tested. Vine vigour was reflected in measured internode length and leaf petiole N content. The average daily N-mineralization rate from soil organic matter (SOM) varied among the sites. Laboratory incubations revealed a positive relationship between soil total N content and average daily mineralizable-N in most sites. However, there are other factors involved in promoting excess vigour those to be taken into account.

Irrigation and Rootstock Effects on the Phenolic Concentration and Aroma Potential of Vitis vinifera L. cv. Cabernet Sauvignon Grapes

Compositional changes of skin and seed phenolic compounds and berry glycosylated aroma precursors were measured in Vitis vinifera L. cv. Cabernet Sauvignon onto 1103P and SO4 rootstocks, in three irrigation regimes (FI, 100% of evapotranspiration; DI, 50% of evapotranspiration; and NI, non-irrigated). The study was conducted in a commercial vineyard of central Greece, in a factorial experiment during two growing seasons (2005-2006). Grape samples were obtained at commercial harvest. The deficit water supply decreased berry size but did not affect the skin/pulp weight ratio. Water limitation, especially pre-veraison, caused a substantial increase of skin anthocyanin concentration, and this effect was independent of water deficit-induced reductions in berry size and vine vigor. Among individual anthocyanins, malvidin-3-O-glucoside was mostly affected by water supply. The rootstock genotype did not affect berry growth parameters and skin polyphenol concentrations. The irrigation regime (mainly post-veraison) and rootstock genotype affected total flavan-3-ol monomers in seed tissue, mainly as a result of variations in the catechin amount. The lower seed phenolic concentration was found in non-irrigated and SO4-grafted vines, probably as a result of the restriction of scion vigor caused by these treatments, thereby altering cluster exposure. Skin and seed tannins were not affected by either rootstock or irrigation. The limited water supply was associated with increased aroma potential at harvest.

Influence of Grapevine Training Systems on Vine Growth and Fruit Composition: A Review

Training a grapevine involves a manipulation of vine form. The type of training may lead to differences in total leaf area and the percentage of leaf area well-exposed to light. Consequently, the ability for a grapevine to photosynthesize efficiently depends upon its training system and the accompanying light microclimate of its leaves. In addition to altering the light microclimate of the canopy, training may impact numerous other variables such as fruit bud differentiation, cluster exposure, vine water status, and leaf transpiration. Modification of vine training systems to achieve balance between vine vigor and yield has led to divided canopy systems that might simultaneously increase yield and improve fruit composition through optimization of canopy light microclimate. Consequently, many training systems have been identified as being capable of improving wine quality through a combination of enhanced canopy and fruit microclimate.

Enhancing the value of field experimentation through whole-of-block designs

Precision agriculture (PA) offers opportunities for the development of new approaches to on-farm experimentation to assist farmers with site-specific management decisions. Traditional agricultural experiments are usually implemented in fields with the least possible soil heterogeneity under the assumption that responses to inputs and inherent variation of the soil are additive components of yield variation. However, because the soil in typical fields is not homogeneous, PA has much to offer. Farmers faced with variable conditions need to optimize their management to the variation over space and time on their farm, a problem that is not solved by conventional approaches to experimentation. New designs for on-farm experiments were developed in the 1990s for cereal production in which the whole field was used for the experiment rather than small plots. We explore the extension of this type of experiment to a vineyard in the Clare Valley of South Australia aiming to evaluate options to increase grape yield and vine vigour. Manually sampled indices of vine performance measured on georeferenced ‘target’ grapevines were analysed geostatistically. The major advantage of such an approach is that the spatial variation in response to experimental treatments can be examined. Linear models of coregionalization, pseudo cross-variograms and standardized ordinary cokriging are used to map treatment responses over the experimental area and also the differences between them. The results indicate that both treatment responses and the significance of differences between them are spatially variable. Thus, we conclude that whole-of-block on-farm trials are useful in vineyards.

Effects of novel hybrid and traditional rootstocks on vigour and yield components of Shiraz grapevines

Background and Aims: The influence of grapevine rootstocks on vine vigour and crop yield is recognized as an integral part of viticultural management. However, the genetic potential of Vitis species rootstock hybrids for vigour and yield control is not fully exploited in Australian viticulture. The effect of 55 novel inter- and intra-species hybrids and five traditional hybrid rootstock cultivars on winter pruning weight, berry size and fruit yield of grafted Shiraz vines is presented. The genetic predictions that resulted from this analysis were used to illustrate how rootstocks that best perform for a combination of traits may be selected. Methods and Results: The use of linear mixed models and residual maximum likelihood procedures took into account repeated measures and spatial variation within a large field trial (720 vines). Over 6 years of assessment, variation of up to 93.9% in winter pruning weight, 81.9% in fruit yield and 21.0% in berry weight between rootstocks was estimated. Conclusions: The effect of rootstock genotype accounted for marked differences in conferred pruning weight, berry weight and fruit yield from trial averages. Comparison of statistical analysis techniques illustrated that the choice of such techniques may influence the outcome of genetic selection from field trial data. Significance of the Study: Such quantification of the variation between vines in vigour, fruit yield and berry size due to rootstock genotype provides a framework for selection of well-performing genotypes for inclusion in advanced generations of the CSIRO vine rootstock breeding program.

Impact of Weed Management Practices on Grapevine Growth and Yield Components

The need for reducing costs and making grape production more sustainable has prompted the search for alternative weed control practices that optimize production while maintaining profits. For this reason, it is imperative to understand how different weed management practices modify vine–weed interactions. In the present study, we evaluated the effect on weed growth and Zinfandel grapevine growth and production of five weed control practices: (1) flumioxazin, (2) simazine, (3) cultivation, (4) cover crop, and (5) untreated control. The herbicide treatments had the lowest weed biomass, followed by the cultivation, being approximately 10 and 2 times lower than the weed biomass of either the cover crop or untreated control treatments, respectively. However, the differences in grape yield were not as evident. In 2006, a rainy year, the herbicides and cultivation treatments did not differ in grape yield, but the cover crop and untreated control had a reduction of approximately 20% compared with the other treatments. In 2007, a dry year, in comparison to the herbicide treatments, the grape yield reductions of cultivation were around 22%, and those of the cover crop and untreated control were around 48%. Although the cover crop reduced grape yield, it suppressed weed species considered important, such as horseweed, panicle willowherb, scarlet pimpernel, and sowthistle. Also, it was concluded that vines can tolerate a certain amount of weed competition, and that properly timed postemergence control actions (e.g., cultivation or POST herbicides) could provide the necessary level of control to obtain the desired yields. However, under limited soil moisture conditions, the use of PRE herbicides could prove important to maintain vine yield and vigor.

Nondestructive Measurement of Grapevine Leaf Area by Ground Normalized Difference Vegetation Index

Vine leaf area index has a great impact on berry quality. This study was conducted to determine whether vine leaf area index could be estimated, and mapped through normalized difference vegetation index (NDVI) ground‐based measurements. The NDVI measurements were performed using a Greenseeker (N‐Tech Industires, Ukiah, CA and Oklahoma State Univ., Stillwater), pointed sideways at the vertical shoot positioned vines [Vitis vinifera (L.)] at Bordeaux, France. Canopy gap fraction and vertical leaf area index (VLAI) measurements were also performed. Plot NDVI maps were obtained by linking the GreenSeeker to a GPS during measurements. The NDVI delivered by the sensor was sensitive to the variations of vertical leaf area index and gap fraction of the canopy, that is, vine vigor. The GreenSeeker was successfully used to carry out a follow‐up of the foliar growth of the vine, but with many precautions. The maps obtained showed relative variations of vigor at an intraplot level, enabling access to relevant information for better vineyard management.

Effect of foliar nitrogen and sulphur application on aromatic expression of &lt;em&gt;Vitis vinifera&lt;/em&gt; L. cv. Sauvignon blanc

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: It is well known that vine nitrogen deficiency can negatively impact on aroma in white wines. Soil nitrogen fertilization enhances aroma expression, but it also increases vine vigour and susceptibility to grey rot. The aim of this work was to investigate the impact of foliar nitrogen as well as foliar nitrogen and sulphur applications on aromatic expression, vigour and susceptibility to grey rot of Vitis vinifera L. cv. Sauvignon blanc.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: The impact of foliar nitrogen (N) and sulphur (S) application on aromatic expression of Vitis vinifera L. cv. Sauvignon blanc has been investigated. On a plot where vine nitrogen status is naturally low and water availability not limiting, foliar nitrogen and sulphur fertilization (10 kg/ha of N and 5 kg/ha of S) increased yeast available nitrogen content. Vine vigour and maturity level of grapes were not modified compared to the control. The wines produced from N+S vines contained more volatile thiols and glutathione. These results were confirmed by a tasting of wines produced with grapes from the experimental plots. Foliar nitrogen fertilization alone (10 kg/ha of N) also increased Sauvignon blanc aromatic expression, but less so than the N + S treatment.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: Foliar N and foliar N + S applications can enhance aromatic expression in Vitis vinifera L. cv. Sauvignon blanc wines without increasing vine vigour and infestation by grey rot.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: Vine nitrogen deficiency can negatively impact on grape aroma potential. Soil nitrogen application can increase vine nitrogen status, but it has several drawbacks: it increases vigour and enhances Botrytis susceptibility. This study shows that foliar N and foliar N + S applications can improve vine nitrogen status and enhance aroma expression in Sauvignon blanc wines without the negative impact on vigour and Botrytis susceptibility. Although this study was carried out on Sauvignon blanc vines, it is likely that foliar N or foliar N + S applications will have similar effects on other grapevine varieties containing volatile thiols (Colombard, Riesling, Petit Manseng and Sémillon).&lt;/p&gt;

The impact of differences in soil texture within a vineyard on vine vigour, vine earliness and juice composition

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: The young alluvial soils of the Wairau Plains, Marlborough, New Zealand, are considered to play an important role in determining this unique wine style. The aim of this experiment was to investigate, within a single vineyard, the impact of soil texture on vine vigour, vine earliness and fruit composition.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Trunk circumference and pruning weights, were greater as the depth to gravel increased. Soil conductivity measurements, using an electromagnetic sensor (EM38) in conjunction with global positioning related well to vine trunk circumference. Where gravels came to the surface, soil temperatures measured at 30 cm depth were consistently higher by 1 to 2 °C (air temperature was unaffected) and vine phenology was more advanced, when compared to the deep silt soils. At harvest, fruit soluble solids and pH were higher and titratable acidity lower when vines grown on shallow soils, but soil type had no significant effect on fruit yield.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions and significance of the study&lt;/strong&gt;: Vine phenology during the growing season and fruit composition at harvest but not yield, reflect changes in soil texture over quite short distances within vineyards on the Wairau Plains. Within a vineyard, the higher the proportion of gravelly soils, the more advanced the vine phenology and the riper the fruit and wine style will exhibit riper (more tropical) and lower unripe (herbaceous) characteristics on a particular date.&lt;/p&gt;

Long term effects of nitrogen and water supply on confered vigour and yield by SO4 and Riparia gloire de Montpellier rootstocks

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: the present study was designed to test the hypothesis according to which rootstock effects on scion growth and yield are related to fundamental physiological traits which are expressed consistently and independently of environmental conditions.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Pruning weights and yield components from two independent rootstock experiments are reported. In the first experiment, the effect of two levels (30 and 70 kgN/ha/year) was studied during 15 years on Cabernet-Sauvignon vines grafted onto SO4 and Riparia Gloire de Montpellier (RGM). In the second one, Cabernet-Sauvignon and Merlot vines grafted on SO4 and RGM were submitted to two levels of soil fertility shortly after plantation: control and high (100 kgN/ha/year + irrigation) and data from the plantation to year 6 were recorded. In both experiments, vine vigour and yield were significantly affected by rootstocks and fertilisation/irrigation treatments. No interaction was recorded. The devigorating effect of RGM in comparison to SO4 was observed in both experiments, regardless of other parameters. Cabernet-Sauvignon was more affected by rootstock than Merlot.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: Rootstock effects on vine vegetative and reproductive development were consistently expressed, indicating that scion-rootstock interactions are governed not only by adaptative, but also by specific physiological traits.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of study&lt;/strong&gt;: This work provides information on scion-rootstock interactions which may be useful in rootstock breeding programs and may help to better choose the rootstock according to the scion and the environment.&lt;/p&gt;

Assaying the potential benefits of thiamethoxam and imidacloprid for phylloxera suppression and improvements to grapevine vigour

Grape phylloxera ( Daktulosphaira vitifoliae, Fitch) is an encroaching problem for the Australian wine industry with four new outbreaks recorded in the past 5 years. Whilst quarantine- and phylloxera-resistant rootstocks are the recommended long-term management strategies, there are at present no short-term options for recently infested vineyards. In this study, an assay for assessing the impact of the systemic insecticides thiamethoxam (Actara ®; two applications at a concentration of 2000 ppm active ingredient) and imidacloprid (Confidor ®; one and two applications at a concentration of 2000 ppm active ingredient) on suppression of phylloxera populations on grapevine roots was developed. Results from in vitro and in planta trials showed that both insecticides resulted in reduced phylloxera numbers and improved vine vigour. Imidacloprid was found to have a greater effect on phylloxera suppression and vine vigour improvement. Therefore imidacloprid has the potential to be successfully used for phylloxera suppression in the field, but will require further validation under field conditions before recommendations can be made. The assay developed provides a screening procedure for future chemical testing against phylloxera.

Influence of Vine Vigor on Pinot noir Fruit Composition, Wine Chemical Analysis, and Wine Sensory Attributes

The relationships among grapevine (<i>Vitis vinifera</i>) vigor variation and resulting fruit composition, fruit chemical analyses, wine chemical analyses, and sensory attributes were investigated. The study was conducted in a commercial vineyard consisting of the same clone, rootstock, age, and vineyard management practices. In 2003, vine vigor parameters were used to designate vigor zones within two vineyard sites to produce research wines. Similar winemaking practices were used. Descriptive sensory analysis and partial least squares (PLS) modeling was done on two-year-old wines. Wines and model extracts were analyzed by HPLC. Significant sensory attributes included earthy, chemical, heat, sweet, sour, bitter, and astringent. Astringency was the most important attribute used to differentiate the wines. Low vigor wines had much higher astringency than high vigor wines. Positively correlated variables included number of seeds per berry, fruit total tannin (mg/kg), and skin tannin (mg/kg), while total flavan-3-ol monomers per seed, total flavan-3-ol monomers per berry, fruit TA, and berry weight were negatively correlated with the sensory attributes. Interestingly, seed tannin was not an important variable in the model. There was a strong relationship between fruit total tannin and wine astringency, which was related to differences in skin rather than seed-derived tannin. There was a strong relationship between measured and predicted astringency.

Influence of Undervine Floor Management on Weed Competition, Vine Nutrition, and Yields of Pinot noir

Four undervine floor management techniques—composted bark mulch, reflective (white) and black geotextile mulches, and mechanical soil cultivation—were evaluated with regard to weed suppression, canopy sunlight regimes, soil temperatures, vine growth, and fruit composition of Pinot noir at an organically managed vineyard in the Finger Lakes Region of New York during 2004 and 2005. Composted bark mulch and black or white geotextiles significantly reduced weed biomass compared with cultivation, but did not affect vine vigor or overwintering primary bud survival in either year. Vines mulched with white geotextile had significantly greater yields, but there were few differences among treatments in ripening time or fruit composition at harvest. The white geotextile increased yields in one year of this experiment, but those yield increases did not compensate for the higher costs of geotextiles compared with the grower’s standard practice of mechanical soil cultivation.

LONG-TERM EFFECTS OF SEEDED COVER-CROP ON VEGETATIVE CHARACTERISTICS, YIELD AND GRAPE AND WINE COMPOSITION OF 'GRECHETTO' GRAPEVINES IN CENTRAL ITALY

The long-term effects of inter-row cover-crop (Festuca arundinacea and Lolium perenne), on canopy characteristics, yield and grape and wine composition were studied in Grechetto G109 grapevines grown in Central Italy under non-irrigated conditions. In a six-year trial (1999-2004), cover-crop as compared to tillage constantly reduced vine vigour and yield, without altering must sugar concentration. Festuca arundinacea and Lolium perenne cover-crop lead to a decrease in vineyard efficiency ranging from 9% (rainy seasons) up to 40% (dry season). In dry seasons berry polyphenols and colour were increased by cover-crop, which fostered ripening, thus advancing harvest and reducing risks of fungi disease onset. On the other hand, grass competition for nitrogen lead to a reduction of assimilable nitrogen concentration in the must. In dry seasons, wine from cover-crop plots showed a decrease in alcohol concentration and a marked increase in total polyphenols and colour. Competitive cover-crop can be used to lower vine productivity, without additional costs, whenever yield limitation is required (i.e. high soil fertility, high vigorous rootstocks and cultivar combination, high bud-load, high rainfall during the season, etc.). Yield reduction depends on the season and can be due to a reduction in bud fertility in the seasons following hot and dry years or to a decrease in berry and cluster weights in dry seasons.