Conventional soil maps represent the distribution of soil attributes across landscapes but with less precision than is needed to obtain the full economic and environmental benefits of site- specific crop management. This study quantifies the spatial variability of three agronomically significant soil attributes: (1) thickness of mollic epipedon, (2) organic matter content (OM), and (3) pH as related to soil survey map units, spectral data, and terrain attributes for a 20 ha field in Montana. Analysis of Order 1 (1:7920-scale) Soil Survey map units indicates substantial variation in all three soil attributes. There was some evidence that similar attribute values were clustered in the field (0.40 - 0.46 Moran's Coefficients). Two spectral band ratios explained 64% of the variation in OM across the field. GPS/GIS-derived wetness index, sediment transport index, elevation, and slope gradient explained 48% of OM variation. Wetness index, slope gradient, and plan curvature combined to explain 48% of the variation in mollic epipedon thickness. Elevation and wetness index explained just 13% of pH variation. Two spectral band ratios, specific catchment area, and wetness index combined to explain 70% of the variation in OM at 66 sampling sites. Four contour map representations of OM illustrate the sensitivity of the final maps to variations in input data and interpolation method.