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54 WINES&VINES August 2017 WINEMAKING PRACTICAL WINERY & VINEYARD To a lesser extent (compared to air temperature), the timing of phe- nology is also influenced by soil temperature. A warm soil can speed up phenology by approximately one week. Warm soil can be an asset in a cool climate, while it can have an undesirable effect on early ripeness in a warm climate. Vine water status Vine physiology is heavily impacted by vine water status. Vine water deficit provokes shoot growth ces- sation and limits berry size. As long as it remains moderate, it also en- hances the accumulation of grape skin phenolic compounds. These conditions favor the production of high-quality red table wines. When water stress is excessive, it can im- pair photosynthesis and provoke stuck-ripening. Vine water status depends on many factors: soil water-holding capacity, rainfall, reference evapo- transpiration (ET 0 ), grapevine variety, rootstock and training system (in particular leaf area). Hence, it is under the combined influence of climate, soil, plant material and training system. Vine nitrogen status Vines absorb nutrients from the soil. Lack or excess in nutrients can impair vine physiology. However, it has been shown that most nutri- ents and soil minerals do not play a major role in terroir expression, with the exception of nitrogen. 10 Vine nitrogen status impacts yield, vigor, shoot growth, berry size, grape acidity, grape sugar content, skin phenolics and grape aroma compounds. Moderate to low vine nitrogen status favors the production of grapes with high quality potential for red winemaking (small berries and high grape skin phenolics). For high-quality white wine produc- tion, vine nitrogen status should be at least moderate, because low nitrogen status can impair the production of aroma compounds, in particular those from the vola- tile thiol family. 5 Measurements of terroir parameters In the past several decades, many tools have been developed to measure major terroir parame- ters. Some of these are easy to implement and can be used at high resolution. They create the opportunity to produce maps, which are very useful in precise vineyard management to opti- mize terroir expression. Soil mapping Soil maps are produced with auger sampling and soil pit studies. Their precision can be significantly im- proved when soil electric tomog- raphy is measured beforehand. 9 Assessment of climatic parameters Climatic parameters are measured with weather stations. Most wine- growing regions dispose of long- term climate data series, which allows studying the vintage effect on grape composition and wine quality and to assess possible long-term trends in climate evolu- tions. 1 However, few studies ad- dress climatic variability within winegrowing regions, which can potentially have a great impact on terroir expression. Recent miniaturization of tem- perature sensors, shelters and data loggers allow measuring temperature variability at a very fine scale. 6 The impact of tem- perature on vine phenology can be assessed with the Grapevine Flowering Véraison model 2 for a wide range of grape varieties. 3 Coupling fine-scale temperature maps to these phenology models can help growers to optimize the choice of plant material in relation to local temperature variability. Vineyard Tools Battery Powered Pruning Shears • 1.25-inch and 1.5-inch cutting capacity models • 15,000 pruning cuts per battery charge • Includes lithium battery, harness, holster and carrying case www.zenportindustries.com | 503-524-7289 Gra ing Tools w zenportindustri Tying Tools & Supplies Harvest Shears ineyard T ols Pruning | Gra ing | Tying | Harvest SPATIAL VARIABILITY OF THE WINKLER INDEX Spatial variability of the Winkler index in the region of Saint-Emilion, Pomerol and surrounding appellations (Bordeaux area) for the 2012 vintage. 7 Degree- days are expressed in degrees Celsius. High: 1,855 Low: 1,674 Winkler Index 2012 (degree days) 0 5 10 kilometers DE RESSEGUIER, L; R. LEROUX; H. QUENOL, M. EVENOU AND C. VAN LEEUWEN