Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 7/1/2007
Publication Date: 3/1/2008
Citation: Corwin, D.L., Lesch, S.M., Farahani, H. 2008. Theoretical insight on the measurement of soil electrical conducitivy. In: B.J. Allred, J.J. Daniels and M.R. Ehsani (editors) Handbook of Agricultural Geophysics. CRC Press. Boca Raton, FL. Chapter 4 pp:59-83. Interpretive Summary: Due largely to the research of scientists at the USDA-ARS George E. Brown Jr. Salinity Laboratory over the past thirty years, the measurement and mapping of soil electrical conductivity (EC) has become a standard measurement to address field- and landscape-scale agricultural and environmental concerns related to soil. Nevertheless, field measurements of soil EC have been and continue to be misunderstood and misinterpreted by researchers, extension and environmental specialists, and farmers. It is the objective of this book chapter in Handbook of Agricultural Geophysics is to clarify the common misunderstandings by discussing the basic theories and principles behind spatial measurements of soil EC, which are often overlooked. Much of the confusion is due to the fact that the EC of the bulk soil must be measured, which is a complex measurement that is influenced by several soil properties including salinity, water content, texture, bulk density, organic matter, and temperature. Instructional information is presented on how these EC surveys need to be done and interpreted in order to characterize soil spatial variability for various agricultural applications. When used correctly to direct soil sampling, maps of soil EC can be used to inventory soil salinity, map water content and texture, assess soil quality, identify areas where reclamation is needed, create maps of site-specific management units, or monitor changes in soil condition due to management.
Technical Abstract: Geospatial measurements of apparent soil electrical conductivity (ECa) have become a standard geophsyical measurement used in agriculture to characterize the spatial variability of soil salinity, water content, texture, and other correlated soil properties. Nevertheless, ECa has been and continues to be misunderstood and misinterpreted by many researchers, extenion specialistis, and consultants. It is the objective of this book chapter in Handbook of Agricultural Geophysics to clarify misconceptions concerning spatial ECa measurements in agriculture by providing the basic principles and theory of the ECa measurement, standard operating procedures for conducting a field-scale ECa survey, and examples of ECa surveys with associated interpretations of the data. Much of the confusion rests on the fact that ECa is a complex physico-chemical measurement that is influenced by the interrelationship of any soil property influencing the electrical conductance pathways including salinity, water content, texture, bulk density, organic matter, and temperature. Instructional information is presented on how these ECa surveys need to be conducted and the ECa data analyzed to characterize spatial variability for agricultural applications. When used correctly to direct soil sampling, maps of ECa can be used to inventory soil salinity, map water content and texture, assess soil quality, identify areas in need of reclamation, delineate site-specific management units, or monitor management induced spatio-temporal changes in soil condition.