Effects of climate variability on irrigation scheduling in white varieties of Vitis vinifera (L.) of NW Spain

Inter-annual climate variability, mainly rainfall temporal distribution, is a critical factor for scheduling irrigation. In order to efficiently manage precision irrigation systems for Vitis vinifera (L.), their effects on plant physiology, and vineyard soils, together with yield and quality parameters, need to be understood. The current study was conducted on two grapevine cultivars from Galicia (NW-Spain), cv. 'Albariño' and 'Godello', during 2012-2014, in two different Designations of Origin (DO): Rías Baixas and Valdeorras. The treatments were rainfed (R) and surface drip irrigation (DI) in DO Rías Baixas, adding subsurface drip irrigation (SDI) in DO Valdeorras, with four replicates (7 plants each). Irrigation was triggered at fruit set, when midday stem water potential (Ψstem) dropped to −0.5 MPa, and stopped 15 days before harvest in DO Valdeorras; but it was managed by the vinegrower in DO Rías Baixas. Different bioclimatic indices were calculated to characterize each season and location. Soil water content and Ψstem were periodically measured to assess vineyard water status. Yield and juice quality attributes were determined. Water productivity indices were calculated to compare locations and cultivars. Differences between DOs were observed regarding bioclimatic indices, which indicated temperate and very cool nights for cv. 'Godello'. In the case of 'Albariño', warmer nights were observed. In DO Valdeorras, the differences between treatments in Ψstem were never higher than −0.19 MPa; whereas they were almost null in DO Rías Baixas. Yield parameters showed a worse overall productive performance for the R treatment, with lower yields in 2012 and 2013. Qualitative parameters were stable over the three growing seasons studied. Adjusting irrigation schedules for a given season using Ψstem measurements and considering the phenological stage of the vine might help to obtain homogeneous harvests, both in yield and quality. Water productivity indices related with grape yield and pruning weight showed that, in a temperate climate, vegetative growth has an important weight in vineyard water use.