Interaction of Irrigation Amounts and Canopy Management Practices on Grapevine Water Relations, Berry Characteristics, Productivity and Wine Composition

A study was continued during the 2002-growing season at three different sites to determine the interaction of irrigation amount and several canopy management practices on leaf, stem and cluster water relations, berry characteristics and productivity. The irrigation amounts were various fractions of estimated vineyard evapotranspiration (Etc), the specific amounts were agreed upon by each grower/cooperator. The canopy management practices included the use of different trellis systems, vine and row spacing, row direction, cluster exposure and leaf removal.The study site in Madera was conducted in a bilateral cordon trained Merlot vineyard. Water was applied at 0.4, 0.8 and 1.2 estimated vineyard water use. Canopy management practices included leaf removal in the fruiting zone either at berry set or veraison (leaves in the control treatment were not removed). Vine water status, as measured by midday leaf water potential, was significantly affected by irrigation amount but not canopy management practice. The amount of light measured in the fruiting zone was affected by both irrigation and canopy practices. Irrigation amount had a significant effect on berry weight, soluble solids, pH, titratable acidity and yield. Canopy management only affected soluble solids and yield. Irrigation amount had a significant effect on anthocyanin content but the canopy management practices did not in 2001.The study site in Livermore Valley consisted of a comparison of two trellis types, VSP versus Scott Henry and the application of different amounts of water (0.375, 0.56, 0.75 and 1.12 times estimated Etc). Irrigation amounts had a significant effect on vine water status. Cluster exposure was greater for the Scott Henry compared to the VSP trellis, regardless of irrigation amount. Both irrigation amount and trellis type affected berry weight, soluble solids and yield. Yield was greater for the Scott-Henry trellis compared to the VSP and it increased as applied water increased. There was a significant interaction between irrigation amount and trellis for juice pH and titratable acidity. Anthocyanins, measured in 2001, were greater as applied water decreased and they were higher for the VSP compared to the Scott Henry trellis.The study conducted in Napa Valley consisted of a comparison of two trellis systems and row spacing using Cabernet Sauvignon on two rootstocks (5C and 110R). During the 2002-growing season, high temperatures and low relative humidity for a couple of days during the later part of June resulted in considerable sunburn of the fruit. Greater than 70%of the clusters in the 1 x 1 m spacing treatment, were sunburned. Absolute amounts were dependent upon rootstock, 5C had more sunburn than 110R. In the Wye trellis, irrigation amount and rootstock significantly affected the amount of sunburn. Vines receiving no applied water had more sunburn than vines irrigated at 75%of ETc. Again, the 5C rootstock had more sunburn than the 110R Rootstock. Measurements later in the season, indicated that ambient temperature in the fruiting zone and cluster temperature were greater in the 1 x 1 m treatment than those in the Wye.