Apparent electrical conductivity response to spatially variable vertisol properties

Abstract

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 14 ha. 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 in Vertisols weathered from calcareous parent materials, allowing for spatial inference of shrink-swell potential which may be useful in distributed hydrology modeling.

Measurement of apparent electrical conductivity of soil and the spatial variability of soil chemical properties by electromagnetic induction

“…Several authors (Corwin and Lesch, 2005;Amezketa, 2007;Triantafilis et al, 2009;Neely et al, 2016) have shown strong correlations between the soil electrical conductivity and the electrical conductivity of extract saturation (CEe, mS m -1 ), the content of organic matter (OM, ) and cation exchange capacity (CEC, ); but in this study the greatest correlation coefficient values were found for OM.…”

“…Apparent electrical conductivity is the ability of a material to transmit or conduct electrical current (Doerge, 2004). It is influenced by various factors of soil such as porosity, dissolved electrolyte concentration, texture, quantity and composition of colloids, organic matter, inorganic C and water content (Machado et al, 2015;Neely et al, 2016). Some research reports that EC a readings are related to soil characteristics and properties such as pH, humidity, texture and CEC (Molin and Rabello, 2011).…”

Soil Moisture Mapping Using Multi-Frequency and Multi-Coil Electromagnetic Induction Sensors on Managed Podzols

“…These findings are similar to the results of this study even though CVs are less than 23% ( Table 2). The CVs of EC a -L, EC a -H, and EC a -38 kHz measurements and measured SMC (Table 2) suggest that EC a values respond to vertical heterogeneity of soil properties [65] such as SMC variability along the soil depth.…”

Spatial Relation of Apparent Soil Electrical Conductivity with Crop Yields and Soil Properties at Different Topographic Positions in a Small Agricultural Watershed

“…However, Peralta and Costa [49] and Neely et al [59] observed strong negative correlation of ECa with soil organic matter and inorganic carbon in coarse-loamy Mollisols and clayey Vertisols, respectively. Calcium, Mg and Na were often positively and moderately to strongly correlated to ECa [16,58].…”