Continuous measurements of grapevine water status in an irrigated vineyard under changing weather conditions

Abstract

The objective of the study was to test the feasibility of stem and shoot hygrometers for the continuous and nearly non-destructive assessment of grapevine water potentials in the field under varying environmental conditions. The experiments took place in a drip-irrigated steep slope vineyard of the wine growing region Franconia (Germany). The experimental site is characterized by calcareous soil and has an average annual precipitation of ~550 mm.

The recording intervals covered by one sensor installation were in the range of several weeks. The measured stem and shoot water potentials showed a close correlation to ambient VPD during the day, thus confirming the weather dependency of midday water potential measurements in contrast to measurements at predawn. While predawn water potential in the non-irrigated control treatment steadily decreased, even small amounts of water applied by drip irrigation always resulted in short-term recoveries of predawn and midday water potential.

Water potential measurements conducted with a Scholander chamber as reference method and those acquired with in-situ hygrometers were in good agreement at the time of predawn water potential. However, at midday the values from the hygrometers were slightly underestimating actual plant water status. In general, the stem hygrometers allowed continuous water potential measurements but for precise results they required accurate installation with contact to the measured tissue and careful isolation against weather influences.