Irrigation of cv. Verdejo: physiologic, agronomic and qualitative effects in the D.O. Rueda (Spain)

Abstract

Irrigation management is a critical aspect for cultivation of white grape varieties in order to regularize grape yield and quality in those regions with a clear water limitation, as most of the Spanish growing regions. In the case of cv. Verdejo, the obvious summer water stress situations lead to irrigation needs , which should be in accordance with the site production potential, the adaptation of cultural techniques and the productive and qualitative objective of the producer or wine company. The application of moderate irrigation was studied from 2012 to 2014, with three different approaches, rainfed (S00), 25% ETo (R25) and 50% ETo (R50), implemented from the end of primary shoot expansion until harvest. The trial was carried out on Verdejo vines grafted on 110R rootstock, planted in 2006 and trellised as a Royat bilateral cordon. The vine distances were 2.60 m x 1.25 m (3,077 plants/ha). The study was conducted in a vineyard located in Medina del Campo (Valladolid, Spain), belonging to D.O. Rueda, and focused on the evaluation of physiological, agronomical and qualitative response to different doses of irrigation. The results showed a positive physiological response to the amount of water applied, more noticeable as the summer progressed, with shoot vegetative growth and vigor being aided by irrigation. Also, fruit yield increased proportionally with the amount of irrigation applied, mainly through the cluster weight, which has primarily varied with the berry weight. As for the grape quality, the response has been variable with the year. Thus, the sugar concentration was benefited by irrigation the first year, but it has been slightly reduced later. The titratable acidity and potassium concentration have shown the contrary effect to sugars over the years. By contrast, as a general tendency, the tartaric acid has shown a tendency to reduction with irrigation and the malic acid to increase.