Issue link: http://winesandvines.uberflip.com/i/853816
56 WINES&VINES August 2017 Assessment of vine water status Many tools have been developed in recent de- cades to measure vine water status. Two are of particular interest because they are precise and easy to implement at reasonable cost: measure- ment of stem water potential in the field or assessment of carbon isotope discrimination on grape juice at ripeness (so-called δ 13 C). 12 Stem water potential is measured with a pressure chamber on leaves, which are bagged with an opaque plastic bag close to solar noon (around 2 p.m.). Repeated measurements provide a very precise assessment of the varia- tions of vine water status in the growing season in relation to climatic (rainfall and evapotranspiration) and soil-related (soil water-holding capacity) parameters. The drawback of this tool is that the number of parcels that can be monitored is limited, which makes it not suitable for spatial repre- sentation of vine water status. The δ 13 C can be measured from grape juice in labs specialized in stable isotope analyzes for between $30 and $50 per sample. It rep- resents the average water deficit of the vine during the first weeks after véraison, when grapes accumulate sugar. Although it does not give precise information on the timing of water deficits, it allows evaluation of vine water deficit intensity in many locations, opening the possibility of creating very pre- cise maps showing variability in vine water status at the intra-block scale. See "Mapping Vine Water Status." Assessment of vine nitrogen status Plant-based measurements are, by far, more powerful compared to soil-based measure- ments to assess vine nitrogen status. Among these, yeast assimilable nitrogen measured on grape juice at ripeness is an easily accessible indicator at low cost. With high-density sam- pling (10 samples per hectare), very precise maps can be obtained showing vine nitrogen status variability at the intra-block level. See "Vine Nitrogen Status Map." Managing terroir parameters Site selection: Site selection is a major tool TOP MAP: SOVIVINS. BOTTOM MAP: TRÉGOAT AND VAN LEEUWEN, UNPUBLISHED WINEMAKING PRACTICAL WINERY & VINEYARD TTB LABEL APPROVALS Low per-label costs Gov't. Liaison Negotiations or Footwork Reasonable Hourly Rates TRADEMARK SEARCHES As Low as $185 Your trade names or designs are searched at the U.S. Patent Office to help establish valuable ownership or avoid costly legal liability. Over 100 years' total staff experience handling every government liaison need for industry. Phone or write for details. 200 N. Glebe Rd., Suite 321 Arlington, Virginia 22203 Phone: (703) 524-8200 Fax: 525-8451 TOLL-FREE 1-800-642-6564 Major Credit Cards Accepted www.trademarkinfo.com Since 1957 GovtLiaison_Dir08 11/29/07 2:00 PM Pag MAPPING VINE WATER STATUS -22.0 -22.4 -22.8 -23.2 -23.6 -24.0 -24.4 -24.8 -25.2 -25.6 -26.0 -26.4 -26.8 Gravel Gravel with deep permanent water table Sand over clay Sandy clay with non-permanent water table Measuring the δ 13 C in grape juice just prior to ripeness in a vineyard in Saint-Emilion, France. Spatial pattern of water deficit is consistent with soil map. The δ 13 C map was obtained by ordinary kriging of 10 measurements per hectare. The δ 13 C values range from -22 p.1000 (moderate to severe water deficit) to -26 p.1000 (no water deficit). Soil Type δ 13 C 0 60 120 meters 0 60 120 meters