Use of Sap-Flow Sensors to Schedule Vineyard Irrigation. I. Effects of Post-Veraison Water Deficits on Water Relations, Vine Growth, and Yield of Shiraz Grapevines

Abstract

Different levels of irrigation based on transpiration data measured using sap-flow sensors were applied after veraison to Shiraz grapevines grown on a two-wire vertical trellis in the Barossa Valley, Australia. Data for the vines of the upper and lower wire were studied separately. The intensity and duration of stress in each treatment was expressed as a water stress integral (Sψ) from the predawn leaf water potentials. Leaf area, yield and post-veraison water use of vines in the different treatments was closely related to Sψ. Irrigation increased grape yields and differences in vine water status after veraison led to differences in the leaf area to fruit weight ratio. It was concluded that data from the sap-flow sensors could be used as a basis for calculating irrigation amounts to influence vine water status, canopy size, and grape yield.