Water potential in cv. Verdejo: response at different day times to the variation of water regime in the d.o. rueda (Spain)

Abstract

Context and purpose of the study ‐ Irrigation management is a critical aspect in grapevine cultivation to regularize grape production and quality in areas of clear water limitation. The scarcity of information implies the need to know the plant water status to make an estimate of the response of cv. Verdejo to the variation of water regime in vineyard cultivation.

Material and methods ‐ Throughout the 2016, 2017 and 2018 seasons, the vine water status was studied through the measurement of leaf and xylem water potential, at different times of the day, as response to the application of three treatments of water regime: rainfed (R0), irrigation of 30% ETo from beginning of veraison (R1) and irrigation of 30% ETo from pea size (R2), in both cases until harvest. The trial was developed with vines of cv. Verdejo, on 110R, planted in 2006 and vertically trellised trained, in the D.O. Rueda (Spain).

Results ‐ The various types of measurement of water potential showed significantly less negative values in the irrigated vines (R2) than in the non‐irrigated ones (R0 and R1) until veraison, with more or less delay, compared to the start of irrigation in R2, depending on the year and on the measurement time. The measurement of xylem water potential, at 12 hs, showed a slight delay in the appreciation of the significant differences favorable to R2. In contrast, the measure at 7 hs in leaves on the shaded side showed greater immediacy in the favorable discrimination to R2 the driest year, 2017. The wettest year, 2018, none of the potential measurement types was able to show significant differences between treatments throughout the entire period in which only the R2 treatment was irrigated. From the beginning of the application of irrigation in treatment R1, at the beginning of the veraison, the various measurements of water potential showed significant differences favorable to the irrigated treatments (R2 and R1) with respect to the rainfed one (R0), with values slightly less negative of R2 than of R1, at all hours of measurement. However, in the wettest year, 2018, the appearance of these significant differences was delayed in the various types of measurement, but more accentuated in the measure of xylem potential, at 12 hs, and in the 9 hs in leaves of the sunny side, while at 12 hs in leaves of the sunny side it was not registered. The measurement of water potential at 7 hs in shaded leaves was slightly more sensitive to the variation of the water regime, besides being more comfortable to execute, than at 9 and 12 hs in leaves to the sun and, in particular, than that of xylem potential, at 12 hs, which also requires the pre‐bagging of the measuring leaf. Therefore, the measurement of water potential at 7 hs in leaves on the shaded side is interesting as a practical indicator of the water status of the vineyard.