Submitted to: World Congress of Soil Science
Publication Type: Abstract only
Publication Acceptance Date: 6/9/2006
Publication Date: 7/9/2006
Citation: Corwin, D.L., Lesch, S.M. 2006. Mapping soil properties using eca-directed sampling. World Congress of Soil Science. Paper No. 56-4 Interpretive Summary:
Technical Abstract: Characterizing spatial variability is an important consideration of any landscape-scale soil-related problem, such as solute transport, precision agriculture, and soil quality assessment, to mention just a few. Apparent soil electrical conductivity (ECa) is a quick, reliable measurement that is frequently used for the spatial characterization of edaphic properties. It is the objective of this paper (i) to present protocols for conducting an ECa survey and (ii) to apply these protocols to map the spatial variability of soil properties involved in a soil quality assessment at a drainage water reuse site. The protocols are comprised of eight general steps. The soil quality assessment was conducted on a 32.4-ha field in California's San Joaquin Valley (SJV) where a mobile electromagnetic induction (EMI) survey was performed following the outlined protocols. The EMI survey consisted of ECa measurements taken at 22,177 locations in April 2002. A response-surface sampling design identified 40 sites where soil-core samples were taken at 0.3-m increments to a depth of 1.2 m. Soil samples were analyzed for a variety of physical and chemical properties associated with soil quality for an arid-zone soil used for the growth of forage (i.e., Bermuda grass) for livestock. Analysis characterized the soil as montmorillonitic, saline, and sodic with ECe (electrical conductivity of the saturation extract) varying from 4.83 to 45.3 dS/m, SAR (sodium adsorption ratio) from 5.62 to 103.12, and clay content from 2.5% to 48.3%. Spatial trends showed high areas of salinity and SAR in the center of the southern half of the study area. Maps of spatial variation of properties associated with soil quality for an arid-zone soil (i.e., ECe, SAR, B, and Mo) are presented. The developed ECa-directed sampling protocols provide the guidelines to assure reliability, consistency, and compatibility of ECa survey measurements and their interpretation when used to map soil properties.