Response of grapevines to irrigation-induced saline–sodic soil conditions

Abstract

The responses of grapevines (Vitis vinifera L.), ungrafted and grafted to Ramsey rootstock, to saline irrigation have been investigated in drip-irrigated trials at Loxton, Dareton and Merbein in the Riverland–Sunraysia region of the southern Murray–Darling Basin. Soil type and climate were similar across the sites and the characteristics of the soils were monitored in relation to salinity treatment. The treatments involved application of defined irrigation water salinities throughout the season at Merbein and Dareton, while at Loxton, a high salinity treatment was applied between flowering and veraison with low salinity being applied in the remainder of the season. Between-site comparisons of the same rootstock or same cultivar in the fifth season of irrigation show that for water of similar salinity (volume weighted electrical conductivity of 1.4–1.6 dS/m), the ion accumulation patterns were not equivalent.

Leaf petiole sodium ion (Na⁺) and chloride ion (Cl^–) concentrations in ungrafted Sultana vines at Dareton were 2-fold those at Merbein, which aligned with differences in electrical conductivity of the soil saturation paste extract. Differences between salinity of soil and ion content of leaves at the 2 sites were attributed to different irrigation management with the estimated leaching fraction at Merbein nearly double that at Dareton. The average EC_e at Loxton was equivalent to that at Merbein. However, the leaf lamina Cl^– in vines grafted to Ramsey rootstock at Loxton was 2-fold that at Merbein and leaf lamina Na⁺ was 10-fold.

Cultivar differences between the 2 sites — Sultana at Merbein and Colombard at Loxton — may explain a small part of the increase in leaf Na⁺ and most of that in leaf Cl^–. However, a far more plausible explanation is that vines at Loxton experienced transient waterlogging which increased their uptake of both Na⁺ and Cl^–, and increased the rate of Na⁺ uptake relative to that of Cl^–. Transient waterlogging was probably caused by a combination of soil sodicity, small excesses in irrigation, and the combination for part of the season of low electrolyte concentration and high sodium adsorption ratio in the soil solution. Under waterlogged conditions, the uptake of Na⁺ relative to Cl^– at Loxton would have been further enhanced by the inherent differences between Loxton and Merbein in the properties of the soil solution. The soil solution at Loxton had a higher Na:Cl ratio.