Partial rootzone drying of Vitis vinifera cv. 'Shiraz' winegrapes in a semi-arid climate

Environmental issues such as prolonged drought have triggered the need to reduce the use of irrigated water to a sustainable level. Novel irrigation methods, like partial rootzone drying (PRD), have increased our understanding of plant physiology with respect to plant water use. A field trial was established in Mildura, Northwest Victoria, Austral-is to determine whether Vitis vinifera L. cv. 'Shiraz' grown in semiarid conditions were actually producing a PRD response, that being a reduction in stomatal conductance with no loss in plant water potential, and then to measure the responses with respect to yield and fruit quality attributes. Treatments consisted of a control irrigated by two drip lines on either side of the vine row (100% control), a deficit treatment irrigated by a single drip line (50% control), and two PRD treatments alternated between single drip lines on each side of the vine row on a 2 irrigation (50% PRD2) and 14 day (50% PRD14) cycle. There were no significant changes in leaf water potential (Psi(L)) between any irrigation treatment for measurements conducted at 1000 h and 1500 h. However, stomatal conductance (g(s)) was significantly reduced at 1500 h for the 50% PRD14 compared with the 100% control. Yield was unaffected across all treatments despite the 50% control and PRD treatments having smaller berry weights and higher total anthocyanin levels compared to the 100% control. Overall the controlled level of water stress did improve water use efficiency whilst being favourable on some of the grape quality attributes.