Sensitivity of Trunk Diameter Fluctuations in Vitis vinifera L. Tempranillo and Cabernet Sauvignon Cultivars

The effects of different applied water amounts on the behavior of parameters derived from trunk diameter fluctuations were studied during three consecutive seasons (2004 to 2006) in a mature vineyard planted with Vitis vinifera cv. Tempranillo and cv. Cabernet Sauvignon in Albacete (Castilla-La Mancha, Spain). Maximum daily trunk shrinkage (MDS) was calculated from trunk diameter fluctuations. The response of MDS to different irrigation treatments varied in the amplitude of the signal between the two cultivars. Tempranillo MDS was significantly higher than that of Cabernet Sauvignon in the period before veraison for the three years. MDS decreased in magnitude after veraison regardless of irrigation treatment and tended to be similar in the two varieties, except for one year where there were cultivar differences in yield caused by differential effects of a frost. irrigation treatment differences in MDS were significant in 2004 and 2005 at pre- and postveraison, while in 2006 they were nonsignificant, possibly due to the very low yield caused by a late frost which differentially affected the cultivars, suggesting that yield level may be another factor to consider when attempting to use MDS for irrigation management. It appears that the use of trunk diameter sensors for irrigation scheduling in winegrapes would require a specific calibration for the different cultivars.