LOCATING SOIL BOUNDARIES USING MAGNETIC-SUSCEPTIBILITY

Topsoil (0 to 5 cm) samples which included three soil series and three drainage classes were taken at 1 m intervals along a 200 m transect through native prairie in southern Oklahoma. Magnetic susceptibility was measured on every sample, particle size distribution and organic matter content on alternate samples, and elevations at 5 m intervals along the transect. Magnetic susceptibility values were larger on the summit and sideslopes, smallest in the drainageway, and related to sand content (parent material) and soil wetness (landscape position). The sand content of the soil followed a similar pattern to the magnetic susceptibility. Clay and organic matter content increased slightly along the transect and did not appear to be related to landscape position or soils. Semivariograms based on magnetic susceptibility, sand, and silt contents displayed ranges of 59 to 64 m, indicating boundaries at approximately 60 and 120 m; these roughly seperated the well- and moderately well-drained soils from the poorly-drained soil. A moving split window technique was used as a numerical method for boundary location. Textural components provided a general indication of the boundaries among the three soil series, but magnetic susceptibility data partitioned the transect with more distinct boundaries which clearly delineated the soil series. Magnetic susceptibility can be measured in situ at numerous locations much more quickly than texture, and additionally it accounts for drainage conditions of the soil. Its use in soil survey looks very promising.