A SOIL DEPTH APPROACH TO SOIL QUALITY ASSESSMENT

Soil quality is a term associated with soil suitability for productivi ty and environmental quality-related uses It is often assessed from qu antitative measurements of soil properties that can exhibit a wide ran ge of variability across the landscape due to differences in soil form ation and erosion processes. Thus, the depth to some profile feature t hat delineates the zone in which most soil processes are restricted to (effective sail depth ESD) must be included in the development of soi l 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 wed to characterize productivity and erodibility, two co mmon indicators of soil quality. Selected soil properties were determi ned for a range of ESD above a fragipan horizon which restricted sail water movement and rooting depths. As ESD decreased from 100 to 20 cm, productivity decreased and erodibility generally increased These adve rse changes in soil quality were attributed to the modification of sev eral properties that were highly correlated with ESD. Therefore, ESD i s considered a reasonably accurate method of assigning a soil quality index to soils that have a limited depth.