EM38 for Measuring and Mapping Soil Moisture in a Cracking Clay Soil

Abstract

Soil moisture content in the crop root zone varies both spatially and temporally. Moisture in this zone is critical to plant development and health, so understanding the variability and dynamics of moisture distribution in this zone is crucial for optimal crop management. The EM38 electromagnetic induction sensor, a tool for measuring apparent electrical conductivity in soils, can be used to infer a range of soil properties, including soil moisture. The ability to configure an EM38 for on-the-go sensing and mapping of soil apparent electrical conductivity (ECa), if related to key soil properties such as moisture content, means high resolution soil maps can be produced that may significantly aid in the management of agricultural fields. This thesis describes an investigation of the EM38 to quantify soil moisture variability in a paddock of homogenous Black Vertosol soil (cracking clay). The research project comprised three main components: (i) an assessment of two 'conventional' soil moisture probes; (ii) an investigation of the relationship between soil moisture, and its vertical distribution, and EM38-dervived ECa readings; and (iii) a brief investigation of the potential of a mobile on-the-go EM38 survey to assess temporal and spatial patterns of paddock-scale soil moisture.