Irrigation effects on the ecophysiological response of Godello cultivar from Valdeorras D.O. (northwest Spain) in 2012

Abstract

In Spain, grapevines were traditionally cultivated under rainfed conditions until recent years. In Galicia, the need for irrigating the vineyards was not a priority until very recently. However, in the last years, an important variation in the frequency, amount and distribution of rainfalls in Galicia has been observed. This caused an increasing interest to know the effects of irrigation in the response of Galician traditional grapevine cultivars. In this context, the aim of this study was to assess the ecophysiological response of Godello cultivar to three different irrigation treatments. The experiment was conducted in the Valdeorras Designation of Origin (D.O.). The field assay consisted of three treatments: rainfed, surface and subsurface drip irrigation. Field measurements of soil water content (at 5, 15 and 60 cm depth) were performed every two weeks using a TDR equipment. Moreover, on the same dates, we monitored leaf water potential at early morning, at midday and, also, the stem water potential using a pressure chamber. Chlorophyll fluorescence measurements were carried out at noon using a portable fluorometer and stomatal conductance was registered by means of a porometer. Soil water content showed a decrease during the season, with a smaller slope in the irrigated treatments. No significant differences were observed among treatments when considering the three parameters of chlorophyll fluorescence (Fv/Fm, PSII and ETR). However, plants under subsurface drip irrigation presented the highest values of stomatal conductance; whereas, those plants under rainfed and surface drip irrigation presented similar values. As for plant water status, stem water potential was close to –1 MPa under rainfed conditions during August; whereas, for the same month, under surface drip irrigation, stem water potential was -0.9 MPa and under subsurface drip irrigation it was –0.8 MPa; the same trend was obtained for soil water content, but without significant relationships between the parameters. This light stress did not cause significant differences on yield among the treatments.