Vol.:(0123456789) 1 3 Acta Geophysica https://doi.org/10.1007/s11600-019-00306-1 RESEARCH ARTICLE - APPLIED GEOPHYSICS Temporal stability of soil apparent electrical conductivity (EC a ) in managed podzols Emmanuel Badewa 1  · Adrian Unc 1  · Mumtaz Cheema 1  · Lakshman Galagedara 1 Received: 23 March 2018 / Accepted: 11 May 2019 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2019 Abstract The spatial variability in soil physical and hydraulic properties for a managed podzol was assessed using soil apparent electri- cal conductivity (EC a ). Two EMI sensors, the multi-coil (MC) and multi-frequency (MF), were adopted for measurement of EC a on a silage- corn experimental plot in western Newfoundland, Canada. Results demonstrated a signifcant relationship between the EC a mean relative diferences (MRD) and the soil moisture content MRD (R 2 = 0.33 to 0.70) for both MC and MF sensors. The diference in depth sensitivity between MC and MF sensors accounted for the variation (0.015 to 0.09) in EC a standard deviation of the relative diferences. A signifcant linear relationship was found between the EC a MRD and sand (R 2 = 0.35 and 0.53) or silt (R 2 = 0.43), but not with clay (R 2 = 0.06 and 0.16). The spatial variability of the EC a -based predictions (CV = 3.26 to 27.61) of soil properties was lower than the measured values (CV = 5.56 to 41.77). These results inferred that the temporal stability of EC a might be a suitable proxy to understand the spatial variability of soil physical and hydraulic properties in agricultural podzols. Keywords Electromagnetic induction · Multi-coil · Multi-frequency · Soil moisture content · Spatial variability Introduction The management of agricultural lands requires the under- standing of the variability of soil properties at feld scale, and it is essential to determine the amount of inputs needed to achieve higher productivity with minimum environmental efects (Serrano et al. 2014). Due to the extensive labor and time required for characterizing soil variability (Shibusawa 2006; Brevik et al. 2016), the use of proxy data has been widely adopted (Rezaei et al. 2016). The electromagnetic induction (EMI) method has been proven to be a valuable technique for collection of proxy data that can quantify soil variability (Corwin 2008; Toushmalani 2010; Doolit- tle and Brevik 2014). The EMI sensors measure the soil apparent electrical conductivity (EC a ) either invasively or noninvasively depending on the confguration of the sensor (Serrano et al. 2014; Neely et al. 2016). The proxy data col- lected using EMI sensors have been used to provide spatial variability of soil properties such as soil moisture content (SMC) (Calamita et al. 2015; Altdorf et al. 2017a, b), soil texture (Heil and Schmidhalter 2012; White et al. 2012), soil bulk density (Altdorf et al. 2016) and available water content (AWC) (Fortes et al. 2015). To efectively quantify the proxy data, newly adopted EMI sensors referred to as multi-coil (MC) and multi-fre- quency (MF) have the potential to measure diferent depths simultaneously. The combination of MC and MF allows easy comparison and detailed data at multiple depth integrals. Both MC and MF sensors operate at vertical coplanar (VCP) or horizontal coplanar (HCP) coil confguration with the help of a control unit and conversion software of the meas- ured frequency (unit: Hz) to proxy EC a (unit: mS/m) (Allred et al. 2005; Altdorf et al. 2017a, b). To assess the full potential of EC a proxy data for soil vari- ability and fll the literature gap on the temporal stability of EC a , recent studies have targeted the temporal changes of EC a (Pedrera-Parrilla et al. 2017). Most researchers have analyzed the EC a mean relative diferences (MRD) through the positive and negative deviations from the spatial mean (Martínez et al. 2010; Zhu et al. 2010; Van Arkel and Kaleita 2014). Furthermore, literature confrms the possibility of obtaining a better representation of clay distribution than of * Lakshman Galagedara lgalagedara@mun.ca 1 School of Science and the Environment, Grenfell Campus, Memorial University of Newfoundland, Corner Brook, NL A2H 5G4, Canada