Transient Rootzone Salinity in Precision Irrigated Viticulture in South Australia.

To improve vineyard water use efficiency and wine grape composition, irrigated viticulture in many New World countries has seen a move from full-cover irrigation techniques to methods of precision irrigation that only supplies water to a small portion of the rootzone. However, this form of irrigation can result in very low leaching fractions and when moderately saline water is applied, the risk of salt accumulation in the root zone is significant.

 

A trial was established in Langhorne Creek, South Australia, to determine how and where salt accumulates in the rootzone of drip irrigated Cabernet Sauvignon during the irrigation season and to what extent this salt is removed by winter rainfall, current and projected under climate change.

To determine spatial and temporal salt accumulation in the rootzone during the irrigation season, soil was sampled for measurement of EC of a saturation extract before and after the irrigation season.

Results indicate that salt accumulates to potentially harmful levels within the vine rootzone as a result of irrigation with moderately saline water.

In addition it was observed that an average volume of rainfall during vine dormancy leached a sufficient proportion of salt from the vine rootzone to maintain a sustainable system. However, in years of below average winter rainfall, rootzone salinity remained high at the commencement of the irrigation season increasing the potential for yield and fruit quality reduction.

TRANSMIT, a two-dimensional model was used to simulate long term salt movement in the unsaturated zone under current and future climates and will be presented.