Submitted to: American Society of Enology and Viticulture Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2011
Publication Date: September 11, 2011
Citation: Shellie, K. 2011. Defining efficient deficit irrigation for winegrape cultivars Merlot and Cabernet Sauvignon under semiarid conditions. American Society of Enology and Viticulture Annual Meeting Abstracts. 62:386A-411A. Technical Abstract: Efficient deficit irrigation balances enhanced berry attributes with acceptable reduction in yield. The present study relates pre and post-veraison midday leaf water potential with the growth and composition of east and west-facing berries. Two deficit irrigation treatments were applied over four growing seasons to vines planted in north-to-south oriented rows under warm, semi-arid conditions. Vines under standard irrigation were supplied with 70% of their estimated water demand. Vines under regulated deficit irrigation were supplied 50% of the standard amount between fruit set and veraison and then the same amount as standard from veraison until harvest. Midday leaf water potential and the diameter of east and west-facing berries were measured weekly. Berry maturity and phenolic composition were measured at harvest. The difference in leaf water potential between irrigation treatments pre and post-veraison for Cabernet Sauvignon averaged 0.3 MPa and the standard treatment averaged -1.0 MPa. Yield in Cabernet Sauvignon under regulated deficit irrigation was reduced 30%, berry fresh weight by 19% and titratable acidity by 16%. The difference in leaf water potential between irrigation treatments for Merlot averaged 0.2 MPa pre and 0.3 MPa post-veraison and the standard treatment averaged -1.2 MPa. Merlot yield under regulated deficit irrigation was reduced 25%, berry fresh weight by 11% and titratable acidity by 9%. In both cultivars, east-facing berries under standard irrigation grew faster than west-facing berries under regulated deficit irrigation. Regulated deficit irrigation increased anthocyanin concentration per gm fresh weight by 14% in Cabernet Sauvignon and 17% in Merlot however content on a per berry basis was higher only in Merlot. West-facing berries of both cultivars contained less anthocyanin per berry than east-facing berries and exposure aspect differences were greatest under regulated deficit irrigation. The most efficient irrigation treatment for Cabernet Sauvignon was the standard and for Merlot was the regulated deficit irrigation.