Influence of the irrigation period in Tempranillo grapevine, under the edaphoclimatic conditions of the Duero river valley

Irrigation of vineyards is a matter of controversial arguments at areas of high quality wine production. Besides, the effects of the water in the plant are closer related to the water availability than to the irrigation regime. In this way, the criteria for irrigation timing can reach very important physiologic and productive consequences to optimize the vineyard management on each environmental situation. An experimental trial has been carried out along the period 2005-2007 in the province of Valladolid (Spain), focused on the study of modification of plant water status (leaf water potential), soil water content, physiologic activity, vegetative-productive behavior and quality expression (berry weight, sugar concentration, pH, total acidity, poliphenols concentration) of the Tempranillo variety in the Duero river valley, through the application of a moderate irrigation doses in two different periods of the vegetative cycle, on a concrete edaphic situation. The treatments applied were the following: 20% ETo from vegetative Growth stopping (G20) and 20% ETo from Veraison (V20), both irrigated until one week before harvest. The vines, planted in 1993, were grafted onto 110R and vertical trellised trained, as a bilateral Royat cordon. Vine spacing is 2.70 m x 1.40 m (2645 vines/ha).
The results have shown some differences due to the irrigation period treatments on the effects related to vine water status and soil water content, physiologic activity, vegetative development, productivity and grape quality in Tempranillo variety. In general, the earlier application of irrigation has favoured vine physiologic activity and leaf development, through the improvement of plant water status, estimated by means of leaf water potential measurement, which have consequently provoked certain increase of yield. On the contrary, the delay of irrigation until veraison stage has shown certain tendency in grape composition to increase sugar concentration, pH and poliphenols index.