A diminished capacity for chloride exclusion by grapevine rootstocks following long-term saline irrigation in an inland versus a coastal region of Australia

Abstract

Shiraz and Chardonnay grapevines that had been initially assessed for Cl- exclusion in the 1996 and 1997 harvest seasons at both Merbein (inland region of Victoria) and at Padthaway (sub-coastal region of South Australia), were re-evaluated in 2003 and 2004 at those same two locations. Both scion varieties were grown either on their own roots or were grafted to one of the following rootstocks: Ramsey, 1103 Paulsen, 140 Ruggeri, K51-40, Schwarzmann, 101-14, Rupestris St George and 1202 Couderc. Both sites had been irrigated with saline water since 1994. The salinity of irrigation water at Merbein was approximately 2.1 dS/m; at Padthaway irrigation salinity varied between approximately 1.6 dS/m and 2.5 dS/m during the survey period. Changes in the Cl--excluding ability of all rootstock/scion combinations between 1996, 1997 and 2003, 2004 were based upon analysis of Cl- concentrations in grape juice and in laminae at harvest, as well as Electrical Conductivity (EC), pH and Sodium Adsorption Ratio (SAR) of the 1:5 soil:water extract. Taking juice Cl- as indicative of rootstock effectiveness for Cl- exclusion, and considering data from Merbein, our analyses demonstrated that overall means for Shiraz juice Cl- increased from around 190 to 427 mg/L over the survey period (7 years). In Chardonnay grapevines at Merbein, overall mean concentrations of Cl- in juice increased from around 70 to around 225 mg/L over 7 years. Significant differences between rootstocks were evident, with some rootstocks at Merbein showing a diminished capacity for Cl- exclusion in 2003 and 2004. By contrast, in Padthaway there was no consistent deterioration in Cl--excluding capacity by rootstocks supporting either Shiraz or Chardonnay as scions. In 2004 there were significant differences between grapevines at Merbein and Padthaway in the concentration of Cl- accumulated, even though the mean soil EC1:5 after harvest for 0–90 cm depth was the same at both sites, namely 0.4 dS/m. Containment of grapevine salinity at Padthaway (relative to Merbein) between 1996/97 and 2003/04 was most likely due to factors such as a lower volume of saline irrigation, double the rainfall and 27% lower pan evaporation.