A soil depth approach to soil quality assessment

ABSTRACT: Soil quality is a term associated with soil suitability for productivity and environmental quality-related uses. It is often assessed from quantitative measurements of soil properties that can exhibit a wide range of variability across the landscape due to differences in soil formation and erosion processes. Thus, the depth to some profile feature that delineates the zone in which most soil processes are restricted to (effective soil depth ESD) must be included in the development of soil quality indices that apply spatially. Our objective was to determine the potential of ESD as an integrator of properties that change with depth and are used to characterize productivity and erodibility, two common indicators of soil quality. Selected soil properties were determined for a range of ESD above a fragipan horizon which restricted soil water movement and rooting depths. As ESD decreased from 100 to 20 cm, productivity decreased and erodibility generally increased. These adverse changes in soil quality were attributed to the modification of several properties that were highly correlated with ESD. Therefore, ESD is considered a reasonably accurate method of assigning a soil quality index to soils that have a limited depth.