An electromagnetic induction method for monitoring variation in soil moisture in agroforestry systems

An understanding of the spatial and temporal patterns of soil water extraction by trees in agroforestry systems has long been seen as an important step towards understanding their functioning. Traditional methods of soil moisture monitoring have been employed with some success but limitations in utilising them efficiently across both time and space have led to restrictions in their use. An electromagnetic induction (EMI) technique has been evaluated and used to study the patterns of soil water extraction from a Grey Vertosol in fallow or cropped fields alongside a Eucalyptus argophloia windbreak near Warra, Qld (26.93°S, 150.93°E). This technique provides methods for minimising error caused by seasonal variations in temperature and the vertical distributions of both soil water and temperature. The calibration developed in this study was successful in describing the observed variations in total soil moisture in the surface 0.9 m of the soil profile (R2 = 0.93, s.e. = 15.3 mm). We conclude that EMI techniques can provide a quick and efficient means for monitoring soil moisture patterns in agroforestry systems when employed under suitable conditions. This paper describes the techniques developed and where they may be employed, the type of information available from the approach, and the likely methods for employing EMI approaches in a wider range of situations.