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58 WINES&VINES August 2017 WINEMAKING PRACTICAL WINERY & VINEYARD HoytShepston_Monthly09 10/31/08 4:44 PM in terroir management. The best vineyard sites for production of terroir wines are lo- cated in moderate to cool climates. In warm climates, cooler locations can be found in north-exposed slopes (in the Northern Hemi- sphere) or at high altitudes. In cool climates, south-exposed slopes might be the best loca- tions to obtain full ripeness. Warm (dry, stony and shallow) soils can, to a certain extent, compensate for a cool cli- mate. 4 Moderately dry climates are best suited for production of high-quality wines. Low soil water-holding capacity (SWHC) can compen- sate in a wet climate, while at least moderately high SWHC is preferable in dry climates. Choice of plant material: The choice of plant material is a major tool to optimize terroir expression. Early ripening grape varieties should be planted in cool climates and late-ripening varieties in warm climates in order to obtain ripeness during the ideal window (Sept. 10- Oct. 15 in the Northern Hemisphere). Timing of ripeness can also, in a more lim- ited way, be influenced by rootstock selection. In dry conditions, only drought-resistant grape varieties should be planted (Grenache, Carignan and Cabernet Sauvignon), and drought-sensi- tive grape varieties should be avoided (Merlot and Sauvignon Blanc). Planting with drought- resistant rootstocks such as 110R is a very cost- effective and environmentally friendly way to adapt vine growing to dry climates. Vineyard floor management and fertiliza- tion: When nitrogen availability of the soil is not well adapted to the type of production, vine nitrogen status can be managed by either cover crop (reduction in vine nitrogen status) or fer- tilization (to obtain a higher nitrogen status). Training system: In cool and wet climates, leaf area per hectare should be high to opti- mize both light interception and vine transpira- tion. High-density planting or divided canopies are accurate ways to obtain high leaf areas. In warm and dry climates, leaf area should be limited on a per-hectare basis to limit transpi- ration. Mediterranean bush vines (gobelet) are perfectly adapted to those conditions. Because leaf area to fruit weight ratio is an important quality factor, those vines cannot be high yield- ing. High yields can only be obtained in dry climates through irrigation. However, irriga- tion may raise issues around water resource management and salt stress in vines. Conclusion Many environmental factors are involved in terroir expression. The effects of climate and soil are complex, and they should be divided into measurable parameters such as tempera- ture and water status. To understand their impact on grape composition and wine quality, these must be ranked in order of importance. Climate primarily acts through temperature, rainfall, Evapotranspiration and sunlight, while soil acts through its impact on water status and nitrogen availability. Temperature, vine water status and vine nitrogen status can be accurately measured at high resolution. This opens up the possibility for fine-tuned vineyard management in order to optimize terroir expression. Among available tools, the choice of plant material adapted to local conditions (grape- vine variety and rootstock), vineyard floor management, fertilization and training systems allow growers to produce high-quality wines expressing distinctive terroir characteristics in a wide range of environmental conditions. This paper was originally presented at the XIth Interna- tional Terroir Congress coordinated by Greg Jones and held in Oregon's Willamette Valley. Cornelis (Kees) van Leeuwen is professor of viticulture and head of the viticulture and enology department at Bordeaux Sciences Agro. His papers are available at www-ecole. agro-bordeaux.fr/people/kees.vanleeuwen. Van Leeuwen is also editor of the scientific journal OENO One and con- sultant for Château Cheval Blanc in Saint-Emilion, France. Jean-Philippe Roby is senior lecturer and researcher at Bordeaux Sciences Agro. His specialization is vineyard management and plant material. He is publishing direc- tor of the OENO One scientific journal and consultant for RdV Vineyards in Virginia. Laure de Rességuier is lecturer and researcher at Bordeaux Sciences Agro researching fine-scale climate variations in vineyards and their impact on vine development and grape ripening. She specializes in geographic information systems and remote sensing. The references for this article are available online at winesandvines.com. SOVIVINS Yeast assimilable nitrogen in grape must was measured prior to harvest in a Haut-Médoc estate in Bordeaux, France. The map was obtained by ordinary kriging of 10 measurements per hectare. VINE NITROGEN STATUS MAP 175 - 200 150 - 175 125 - 150 100 - 125 75 - 100 50 - 75 25 - 50 0 - 25 Yeast available nitrogen (mg/L) 0 100 200 meters