The role of EM38 in land and water management planning on the Tragowel Plains in Northern Victoria

Abstract

Geonics EM38 instruments have been used extensively in the Tragowel Plains of northern Victoria, Australia, for large-scale root zone soil salinity mapping of irrigation farms. Baseline soil salinity surveys enable landholders to identify the saline areas of their properties, providing key information to guide farm management and investment decisions. EM38 surveying has played a pivotal role in the successful implementation of the Tragowel Plains Land and Water Management Plan, which requires that a soil salinity survey be completed before a landholder can apply for other salinity-management grant schemes administered by the Plan. The Geonics EM38 uses inductive electromagnetic detection of depth-weighted conductivity in the upper 5 metres of the soil profile. Soil conductivity readings are affected by a range of factors in addition to salinity, such as soil moisture content, clay content, clay mineralogy, temperature, and instrument drift. A robust instrument calibration process was developed and implemented, so that readings from different instruments and surveys completed in different years could be directly compared, and so that instrument readings could be directly related to crop responses to soil salinity. A survey methodology was also developed that provided data at appropriate spatial resolution for farm management decisions, that was cost effective, and that trained and employed local people for much of the field work. As a result, EM38 soil salinity surveys have been widely adopted as a fundamental tool for farm management in the Tragowel Plains, and extensive EM38 soil salinity surveying has been undertaken in other irrigation areas of northern Victoria.