Variation of Soil Properties in a Mollisol Profile Wall

摘要

Soil variation was investigated in a Mollisol soil profile wall in south central Wisconsin, USA. The soil was classified as a fine-loamy, mixed, superac-tive, mesic Pachic Argiudolls. Data were collected from a 1 x 1 m soil profile wall that was divided into a 10 x 10 cm raster. The following measurements were made: volumetric moisture content, soil pH, soil organic carbon (SOC) concentration, and elemental analysis of Al, Ca, Fe, Mn, P, Si, Ti, and Zr by portable X-ray fluorescence (pXRF). Spatial variation of soil properties was analyzed and mapped. All the soil properties demonstrated horizontal variation within the soil profile. The extent of horizontal variation changed with depth. The magnitude and direction of these changes showed no generalpattern, differing between the soil properties. The SOC concentration showed constant horizontal variation at all depths except 70-80 cm. The soil pH demonstrated the lowest horizontal variation in the top 30 cm of the profile. The horizontal variation of Fe concentration tended to increase with depth. Soil property depth functions showed considerable variation between vertical transects. Only the SOC concentration and the soil pH demonstrated fairly consistent responses to changes in depth. The soil showed spatial variation within soil horizons. The soil pH and the Fe concentration showed low within-horizon variation in all soil horizons. SOC concentration showed moderate within-horizon variation in the Apl horizon and high within-horizon variation inthe Bt horizon. Overall, the Bt horizon contained the greatest spatial variation. All soil horizons contained high within-horizon variation of at least one soil property. These results have some implications for sampling pedons.