Sodium Accumulation in Sparsely Vegetated Areas of Native Grassland in Kansas: A Potential Need for a Paranatric Diagnostic Horizon

摘要

Small areas (usually =10 by 10 m in diameter) of short, sparse, or low-quality range-land vegetation are commonly present within the map units of soil series mapped on upland interfluves or in upland depressions of the Bluestem Hills Major Land Resource Area (MLRA 76). Because of the poor vegetation, soil scientists commonly assumed that these areas result from Na~+, so they were mapped as Natrustolls. But, upon laboratory characterization, few pedons met the natric diagnostic horizon criteria. Therefore, the objectives of this study were to examine the morphology and Na~+ content of several small areas of sparse, poor vegetation in native grass uplands of the Bluestem Hills Major Land Resource Area to determine if these areas meet the natric diagnostic horizon criteria and examine profile or landscape features that would make detecting the presence of a natric diagnostic horizon more predictable. Eleven pedons were investigated, sampled, and characterized in the laboratory for particle size, exchangeable Na~+ percentage (ESP), and other characteristics. Two of the 11 pedons met the natric diagnostic horizon criteria, and greater maximum profile ESP values were observed within the shallowest pedons (i.e., those < 1 m to bedrock; Pr > F 0.2533). Elevated ESP values ranging from = 5 to 14% ESP were observed for eight of the other nine pedons. The ESP values were greatest in the horizons with the finest textures. The presence of short, sparse, poor-quality rangeland does not appear to be an appropriate visual cue for mapping soils that contain natric horizons but is an indicator of elevated ESP levels. Therefore, creation of either a paranatric diagnostic horizon or a Natric Argiustolls subgroup for soils with moderate levels of Na~+ might be a suitable solution useful for soil scientists in the field.