Salinity

The term salinity refers to the presence of soluble salts in water and soil systems. Salinity in the plant root zone can have a major impact on the performance of a crop and is arguably the biggest threat to irrigated agriculture.

Photo: Wine Australia

The sources of soluble salts that can accumulate in the soil water beneath grapevines include;

• Salt imported to a field via irrigation water
• Saline ground water
• Weathering of soil minerals, organic materials and the underlying rock in a vineyard
• Ocean-derived salts blown inland and carried to ground in rain and/or dust
• Soluble nutrients and ameliorants such as fertilisers and gypsum that are applied to soil
• Cleaning agents added to drip irrigation systems (e.g. the use of sodium hypochlorite is a source of chloride that adds to the salt load of irrigation water).
• Salinity is commonly measured as the Electrical Conductivity (EC) of a solution. EC is a measure of the ability of a liquid to pass an electric current; it increases as the salinity (salt concentration) of a liquid increases. EC is commonly given in units of dS/m (deci-Siemens per metre).

Salinity can be measured directly from a sample of irrigation water but is measured in soil using either one of two methods: saturated paste extract (ECe) or, the inexpensive but less reliable 1:5 soil water extract (EC1:5).

A soil is defined as being saline when the level of salinity of soil water (concentration of ions) adversely affects plant growth. However, plants have different susceptibilities to soil salinity. In Australia, soil salinity is predominantly due to salts of sodium: sodium chloride (NaCl), sodium carbonate (Na₂CO₃) and sodium bicarbonate (NaHCO₃). While all salts contribute to a salinity effect, some salts have beneficial effects on crops like fertilisers and gypsum.

Resources in this section provide advice on how to manage salinity in the vineyard.