Root Zone Salinity Risks in the Lower Murray Districts

Due to improved irrigation management and system upgrades, the field application efficiency (FAE) in the Lower Murray horticultural districts has risen from about 50 to 85 % during the past 2 decades. Consequently, the drainage volumes have reduced from about 50 % to 15 % of water applied. Under steady state conditions, the salinity in the root zone can be estimated from salinities of the irrigation water and the leachate (i.e. extra irrigation water applied which drains out of the base of the root zone). For this estimate it is assumed that the leaching water uniformly displaces the (saline) soil water in a ‘piston ’ flow manner. Despite the relatively low salinity of the River Murray flows in the past five years, growers practicing ‘precision ’ irrigation expressed concern about the gradual, but visual accumulation of salinity in the root zone of drip irrigated vineyards in particular. A ‘Tri-State Salinity ’ syndicate of Government agencies from western NSW, Victoria and South Australia (with support from federal agencies) was formed to generate new knowledge for managing root zone salinity hazards by undertaking a 3 year laboratory and field scale studies. Besides assessing the risk of salinity accumulation under precision irrigation, the project team is working on strategies fo