Terroir effects on the response of Tempranillo grapevines to irrigation in four locations of Spain: agronomic performance and water relations

We report the effects of different drip irrigation treatments on the agronomic performance and water relations of Tempranillo grapevines, pruned to a bilateral cordon, trained to VSP and under similar cultural practices, in four different locations of Spain, during the 2009-2011 seasons. In three locations (Requena, Badajoz and Valladolid) a pre-veraison deficit irrigation strategy (DIP, where irrigation was withheld until a threshold of midday stem water potential, Ystem was reached, and later irrigated at full ETc) was compared to rain-fed vines; while in the fourth location (Albacete), DIP was compared to a sustained deficit irrigation (SDI, irrigated at 33% ETc season long). In all locations, except Valladolid, another treatment irrigated at full ETc season long was also studied. Results show that rain-fed vines suffered severe water stress in most seasons and sites, reaching Ystem values of up to -1.5 MPa. Pooled over seasons the seasonal water application in the DIP strategy, varied largely among locations (between 76 and 250 mm), but produced a similar increase of relative yield in all sites (by 43 to 48%), mainly due to increased berry size and cluster weight. DIP compared to rain-fed vines also increased leaf area and pruning weight but in different proportion depending on site. Irrigation at full ETc, compared to DIP, only produced small and in most cases non-significant increases in these variables. Pooling data over sites, Ystem was well related with vine yield, indicating that it allows the integration of a large part of the on-site specific characteristics affecting vine yield. However, vine balance and other agronomic parameters varied largely among locations, showing the importance of the interaction between terroir and irrigation in affecting vine performance. Reasons for the differences in behaviour among sites are discussed.