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Application of Soil Electrical Conductivity to Precision Agriculture

Theory, Principles, and Guidelines

USDA-ARS, George E. Brown, Jr., Salinity Lab., 450 West Big Springs Rd., Riverside, CA 92507-4617

View larger version (28K): [in a new window]   Fig. 1. Diagram of the basic suction cup extractor setup for sampling the soil solution. Taken from Corwin (2002a).

View larger version (25K): [in a new window]   Fig. 2. Schematic of the porous-matrix salinity sensor. Taken from Corwin (2002b).

View larger version (88K): [in a new window]   Fig. 3. Soil electrical conductance pathways. 1 = liquid, 2 = solid–liquid, and 3 = solid. Modified from Rhoades et al. (1989).

View larger version (18K): [in a new window]   Fig. 4. Schematic of Wenner array electrodes. C1 and C2 represent the current electrodes, P1 and P2 represent the potential electrodes, and a represents the interelectrode spacing. Modified from Rhoades and Halvorson (1977).

View larger version (120K): [in a new window]   Fig. 5. Equipment layout of the Wenner array technique. Taken from Rhoades and Oster (1986).

View larger version (117K): [in a new window]   Fig. 6. Electrodes mounted in a fixed array.

View larger version (121K): [in a new window]   Fig. 7. Mobile fixed-array equipment for the continuous measurement of apparent soil electrical conductivity.

View larger version (13K): [in a new window]   Fig. 8. Principle of operation of the electromagnetic soil conductivity meter.

View larger version (82K): [in a new window]   Fig. 9. Handheld Geonics EM-38 electromagnetic soil conductivity meter (top) lying in the horizontal orientation with its coils parallel to the soil surface and (bottom) lying in the vertical orientation with its coils perpendicular to the soil surface.

View larger version (81K): [in a new window]   Fig. 10. Mobile dual-dipole electromagnetic induction equipment for the continuous measurement of apparent soil electrical conductivity.

View larger version (84K): [in a new window]   Fig. 11. Close-up of the sled that houses the dual-dipole EM-38 for the mobile electromagnetic induction vehicle.

View larger version (19K): [in a new window]   Fig. 12. Cumulative relative contribution of all soil electrical conductivity, R(z), below various depths for the EM-38 apparent soil electrical conductivity reading when the device is held in a horizontal (parallel) and vertical (perpendicular) position. Taken from McNeill (1980).

View larger version (70K): [in a new window]   Fig. 13. Detailed mobile Wenner apparent soil electrical conductivity (ECa) survey of Quarter Section 10-2 (roughly 70 ha) of the Broadview Water District in the San Joaquin Valley of central California.

View larger version (68K): [in a new window]   Fig. 14. Mobile EM-38 apparent soil electrical conductivity survey of 2396 ha of the Broadview Water District. EMv, electromagnetic induction measurement in the vertical coil-mode configuration.