Apparent electrical conductivity response to spatially variable vertisol properties
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2015 Elsevier B.V. Though much has been done to understand proximally-sensed bulk apparent electrical conductivity (EC a ) in agricultural soils, many of the soil properties identified to be mappable using these techniques, such as salinity and clay content, are not expected to drive EC a response in a non-saline Vertisol. In Vertisols, agrillipedoturbation creates meter-scale variability in soil moisture and chemical properties associated with gilgai features, and if developed from calcareous parent material, can exhibit meter and landscape scale variability in inorganic C content. The ability to map inorganic C may be especially useful in a Vertisol due to its strong correlation with shrink-swell potential. The overall goal of this project was to investigate the potential for mapping inorganic C using EC a surveys in a calcareous Vertisol, with the future goal of mapping shrink-swell potential on these landscapes. On a 40- by 50-m field with intact circular gilgai, EC a was mapped under both moist and dry soil conditions. Soil samples were taken for water content, clay content, inorganic C content, salinity, and depth to parent material. Under moist soil conditions, the strongest correlation to EC a was inorganic C content (r=-0.63), followed by water content (r=0.49); however, under dry conditions, only inorganic C content was significant (r=-0.60). In addition, EC a surveys and inorganic C samples were taken for two larger watersheds of 10 and 14ha. Again, inorganic C content was significantly and reliably correlated to EC a for both fields, and the resulting regression slopes and intercepts were not significantly different between watersheds, though the surveys were conducted at different times. Results suggest that EC a can be used to map inorganic C content in Vertisols weathered from calcareous parent materials, allowing for spatial inference of shrink-swell potential which may be useful in distributed hydrology modeling.
