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Title: Geophysical techniques for assessing soil salinity across multiple scales

Author
item Corwin, Dennis
item LESCH, SCOTT - Riverside Public Utilities
item SCUDIERO, ELIA - University Of California

Submitted to: Fast Times: News for the Near Surface Geophysical Sciences
Publication Type: Trade Journal
Publication Acceptance Date: 12/30/2017
Publication Date: 12/31/2017
Citation: Corwin, D.L., Lesch, S.M., Scudiero, E. 2017. Geophysical techniques for assessing soil salinity across multiple scales. Fast Times: News for the Near Surface Geophysical Sciences. 22(4):43-49.

Interpretive Summary: The worldwide extent of salt-affected soils is estimated to be 350-400 Mha with an estimated annual global income loss due to salinity of US$ 12 billion. Mapping and monitoring soil salinity from field to regional scale is crucial for the control of salinity, crop selection, soil quality and health assessment, reclamation, and assessing degrade water reuse impacts. Over the past 3 decades, scientists at the U.S. Salinity Laboratory have developed proximal sensor (i.e., electrical resistivity and electromagnetic induction) and remote imagery (i.e., MODIS and Landsat 7) approaches for mapping and monitoring soil salinity at multiple scales: (1) field (< 3 km2), (2) landscape (3 to 10 km2), and (3) regional (10 to 105 km2) scales. Guidelines have been developed for each of the three scales. The approaches are based on geospatial measurements of apparent soil electrical conductivity (ECa), which is the bulk conductivity of the soil and is a complex measurement influenced by a variety of soil properties, including salinity, texture, water content, bulk density, clay mineralogy, and organic matter. The purpose of this article is to provide an overview of the salinity assessment approach used at each scale and to show typical salinity maps over multiple scales resulting from their use. The awareness of these approaches is of benefit to agricultural geophysicists, cooperative extension specialists, ag consultants, producers, soil survey specialists, and natural resource specialists and decision makers.

Technical Abstract: The global impact of soil salinity is daunting with an estimated 350-400 Mha of salt-affected soils causing an estimated global income loss of US$ 12 billion. Mapping and monitoring soil salinity from field to regional scale is crucial for site-specific salinity and irrigation management, crop selection, soil quality and health assessment, reclamation, and assessing degrade water reuse impacts. Over the past 3 decades, Corwin and colleagues at the U.S. Salinity Laboratory have developed proximal sensor (i.e., electrical resistivity and electromagnetic induction) and remote imagery (i.e., MODIS and Landsat 7) methodologies for assessing soil salinity at multiple scales: (1) field (< 3 km2), (2) landscape (3 to 10 km2), and (3) regional (10 to 105 km2) scales. Protocols have been developed for each of the three scales. The approaches are based on geospatial measurements of apparent soil electrical conductivity (ECa), which is the bulk conductivity of the soil and is a complex measurement influenced by a variety of soil properties, including salinity, texture, water content, bulk density, clay mineralogy, and organic matter. The three approaches are: (1) ECa-directed soil sampling (field scale), (2) analysis of co-variance (ANOCOVA) approach (landscape scale), and (3) satellite imagery combined with ECa-directed soil sampling (regional scale). The purpose of this article is to provide an overview of these three salinity assessment technologies and to show typical salinity maps over multiple scales resulting from their application. The awareness of these approaches is of benefit to agricultural geophysicists, cooperative extension specialists, ag consultants, producers, soil survey specialists, and natural resource specialists and decision makers.