RT Journal Article
SR Electronic
T1 Determination of Evapotranspiration and Crop Coefficients for a Chardonnay Vineyard Located in a Cool Climate
JF American Journal of Enology and Viticulture
JO Am. J. Enol. Vitic.
FD American Society for Enology and Viticulture
SP ajev.2014.12104
DO 10.5344/ajev.2014.12104
A1 L.E. Williams
YR 2014
UL http://www.ajevonline.org/content/early/2014/01/21/ajev.2014.12104.abstract
AB A study was conducted in a Chardonnay vineyard located in the Carneros district of Napa Valley to derive vineyard evapotranspiration (ETc) and seasonal crop coefficients (Kc) values. The vineyard was planted on 2.13 m rows and a vertical shoot positioning trellis was used. Vineyard ETc was measured using the soil water balance technique. Soil water content (SWC) was measured in ¼ of an individual vine’s soil profile (six access tubes per site) down to a depth of 2.75 m. In addition, vines were irrigated with applied water amounts at 0.25, 0.5, 0.75, 1.0 and 1.25 of estimated vineyard ETc. Vineyard ETc the first year of the study was approximately 400 mm. Thereafter calculated vineyard ETc (the product of reference ET (ETo) and the Kc) ranged from 346 to 503 mm per season. Midday leaf water potential (Ψl), leaf net CO2 assimilation rate (A) and stomatal conductance (gs) were used to indirectly validate estimated ETc (to determine that vines were not stressed for water) and the derived Kc values. Midday Ψl, A and gs were linearly related with applied water amounts and SWC across irrigation treatments and years. The diurnal measurements of A and gs resulted in differences among irrigation treatments, from early morning until late afternoon, with significant differences among treatments dependent upon actual applied water amounts. The results from this study are the first in which vineyard ETc has been measured on vines grown at a cool vineyard site in California. Estimates of ETc from this study would be valid for a vineyard with a row spacing of 2.13 m and the canopy vertically positioned using a maximum Kc of 0.74.