WATER USE RESPONSES OF SHIRAZ VINES UNDER PARTIAL ROOT ZONE DRYING IN A WATER-LIMITING ENVIRONMENT

Abstract

The response of vines to deficit irrigation can be strongly influenced by variety, environmental and management factors such as climate, soil type, irrigation frequency, and amount of water applied. In the 2003/2004 season water was applied at two levels (0.9 and 0.45 ETc) either as partial root-zone drying (PRD) or as conventional drip irrigation (CI) to field-grown Shiraz vines in north-eastern Victoria, Australia. Application of PRD to vines resulted in a unique physiological response distinct from conventional irrigation, with PRD reducing water loss from the canopy under conditions of high evaporative demand. When water availability was not limited (i.e. shortly after irrigation events) PRD vines tightly regulated water loss from the canopy at high and low vapour pressure deficit (VPD). Measurements of stomatal conductance throughout the season suggest that for most of the experiment all vines experienced some degree of water stress. Limited water availability, low to medium vigour vines, restricted root development and high evaporative demand were all factors in the vine's response to PRD. The amount of water applied was the dominant influence on vine yield and vegetative growth in these experiments but there was a clear distinction between PRD and CI in the way that vines responded to evaporative demand.