USING THE EM38 TO MEASURE THE EFFECT OF SOIL-SALINITY ON EUCALYPTUS-GLOBULUS IN SOUTH-WESTERN AUSTRALIA

Landholders in the > 600 mm p.a. rainfall zone of south-western Australia are establishing small (< 10 ha) plantations of Eucalyptus globulus near saline seeps to lower groundwater levels and obtain additional income from timber and pulp. Soil salinity (as measured by Geonics electromagnetic induction meters) reduced the survival and growth rate of different-aged E. globulus at five sites. E. globulus can survive moderate soil salinities [apparent electrical conductivity (EC(a)) as measured by a Geonics EM38 in the horizontal position (EM38H) up to 150 mS/m]. However growth rates declined at 50 to 75 mS/m. A combination of soil salinity and waterlogging caused a reduction in growth rate at 25 mS/m. Plantings up to 14 years old were adversely affected by continuing rises of the watertable and increased salt concentrations around the roots. Adequate site investigations (EM38, depth and salinity of watertable) will reduce the risk of establishing small plantations low in the landscape. Many existing plantations have been established too close to saline seeps and are now showing evidence of growth decline and stress associated with soil salinity. The Geonics EM38 is suitable for advisers and farmers to assess sites rapidly, before planting E. globulus.