Evaluation of seasonal water use and crop coefficients for 'Cabernet Sauvignon' grapevines as the base for skilled regulated deficit irrigation

Water consumption of wine grapevines (Vitis vinifera 'Cabernet Sauvignon') was measured during three consecutive growing seasons (2012-2014) using 6 drainage lysimeters. The lysimeters (1.5 m³ each) were installed within a two-hectare commercial vineyard in a Mediterranean region in the central mountain region of Israel. Water consumption of the lysimeter-grown vines (ET_c) was measured daily and reference evapotranspiration (ET_o) was calculated from regional meteorological data according to the Penman Monteith equation. Seasonal curves of crop coefficient (K_c) were calculated as K_c = ET_c/ET_o. Maximum ET_c values (weekly average) in different seasons ranged from 7.5 to 6.64 mm day^-1 and seasonal ET_c (from DOY 99 through DOY 288) ranged from 746 to 780 mm over the growing seasons. Leaf area index (LAI) was measured weekly using the SunScan Canopy Analysis System. Maximum LAI ranged from 1.36 to 1.16 m² m^-2 for the 2012-2013 seasons, the seasonal LAI pattern was quite similar to control vines grown in the surrounding vineyard. A linear curve relating K_c to LAI (R² values ranged from 0.76 to 0.85) is proposed as the basis for efficient irrigation management. Some of the differences in ET_c and K_c values that were observed are different from those obtained in table grapes (Williams et al., 2003; Netzer et al., 2009) and wine grapes (Picón-Toro et al., 2012) is explained by the different canopy size and architecture.