Effect of reduced irrigation on growth, yield, ripening rates and water relations of Chardonnay vines grafted to five rootstocks

Background and Aims: In the first decade of the 21st century, drought within the Murray-Darling Basin has reduced the amount of water available for irrigation. We investigated whether the response of vines to reduced irrigation was modified by rootstock. Methods and Results: Reduced irrigation (5 versus 8 ML/(ha·year)) was applied to Chardonnay vines grafted to five rootstocks (Ramsey, 140 Ruggeri, 1103 Paulsen, 110 Richter and K51-40) for four seasons. It decreased the yield from 29.3 to 26.7 kg/vine, and increased the irrigation water use index (IWUI) from 4.7 to 6.6 t/(ha·ML), but gains in this index declined as the trial progressed. The values of mid-afternoon leaf water potential were not affected by reduced irrigation, but leaf CO2 assimilation declined from 13.1 to 11.7 μmol/(m2·s). These effects were independent of rootstock. Reduced irrigation did not increase soil salinity (ECe) or vine tissue Na and Cl concentrations. Vines on Ramsey and 1103 Paulsen rootstocks had higher yields, 32.2 and 30.0 kg/vine, respectively, and the highest IWUIs, 5.9 and 5.5 t/(ha·ML). In two of the three seasons, reducing irrigation did not affect the rates of ripening (°Brix/growing degree days) excepting vines on 1103 Paulsen. Ripening rates varied by 1.5-fold between seasons. Conclusion: The yield and growth responses of Chardonnay vines to a 35% reduction in irrigation were not modified by rootstock. Significance of the Study: Reducing irrigation did not lead to a build-up of soil salts. The response of vines to reduced irrigation on rootstocks rated as having good drought tolerance was the same as that for vines on a rootstock rated as having poor drought tolerance. © 2008 South Australian Research and Development Institute.R.M. Stevens, J.M. Pech, M.R. Gibberd, R.R. Walker, J.A. Jones, J. Taylor and P.R. Nichola