Integrating the carbon and water economies of grapevine for optimal management in challenging environments

Changes in global climate and decreased water availability over the past 20 years in Australia have prompted research into the short and long term effects of environmental stresses on grapevines and their resilience to those stresses. The long-term effects of water stress on grapevine physiology and productivity and in particular on the way carbohydrates are assimilated and stored in the plant are still not well understood. Furthermore there are no studies to date that have examined in detail the recovery process after long term deficit irrigation. The main objectives of this project were to: i) characterise the impact of significant reductions in irrigation on vine physiology and productivity over a 3-4 year time frame, ii) determine the way water and carbon economies of the grapevine are integrated under these conditions, iii) obtain information on the physiology of vines in recovery after severe water stress has been applied and conditions revert to normal, iv) develop new vine stress monitoring tools. The main field study comprised six irrigation regimes imposed on mature Chardonnay vines on Ramsey rootstock, growing in a warm to hot semi-arid environment. The irrigation regimes consisted of Control (100%) (approx. 5ML ha-1 season-1 typical for the region) and reductions to 50%, 30%, 20% and 10% from the control, which constitute sustained deficit irrigation (SDI). The reduction consisted of reduced frequency of irrigation rather than reduced depth at each irrigation event. Normal irrigation was provided up until fruit-set. One treatment included a reduced irrigation depth but same frequency as controls (30%D). After the 2008-09 season, one section of each irrigation treatment was restored to control irrigation levels in order to study the recovery after reduced irrigation. Vine water stress and gas exchange were monitored at key stages in addition to standard berry development, berry composition, yield and yield components during the trial. Trunk, leaf and root samples were collected at key stages to be analysed for non-structural carbohydrate (NSC) concentration. Mini-rhizotron tubes were installed to examine the dynamics of root growth.