Evaluation of the EM-38 to Map Sodium-Affected Soils in the Northern Great Plains.

Sodium-affected soils (SAS) cover over 10 million acres in the Northern Great Plains. Improving the classification, interpretation, and mapping of SAS is a major goal of the USDA-NRCS as Northern Great Plains soil surveys are updated. Electromagnetic conductivity (ECa) as measured with the EM-38 has shown promise for mapping SAS, however, this use of the tool needs additional evaluation. This study used an EM-38 MK2-2 meter (Geonics Limited, Mississauga, Ontario), a Trimble AgGPS 114 L-band DGPS (Trimble, Sunnyvale, CA) and the RTmap38MK2 program (Geomar Software, Inc., Mississauga, Ontario) on an Allegro CX field computer (Juniper Systems, North Logan, UT) to collect, observe, and interpret ECa data in the field. The ECa map generated on-site was then used to guide collection of soil samples for soil characterization and to evaluate the influence of soil properties in SAS on ECa as measured with the EM-38. Results of the soil analysis and the relationships between SAS properties and ECa will be discussed.