Management-dependent properties and pedotransfer functions for soil map unit characterization.

摘要

Soil as a dynamic natural resource is important both for biomass production and maintaining environmental quality. There is interest in evaluating its near-surface properties under different management practices in order to improve interpretations. Near-surface soil properties under hayland, woodland, no-tillage and conventional tillage systems for Ultisols in the Appalachian Plateau Coastal Plain regions of Alabama were analyzed in this study. Research sites were located at the Sand Mountain Research and Extension (SMREC) and the E. V. Smith Research (EVSRC) Centers.; Assessment of soil quality involves characterization of the management-dependent soil properties that serve as indicators of a soil's capacity for agricultural production and environmental quality. These properties are sensitive to change by land use and management. In this study, management-dependent soil properties including bulk density, water dispersible clay, infiltration rate, saturated hydraulic conductivity, soil water retention, water stable aggregates, extractable bases, cation exchange capacity, soil organic carbon, total nitrogen, particulate organic matter carbon, mineralizable carbon and nitrogen, dehydrogenase activity, and soil microbial biomass carbon were measured.; Results showed that more intensive cultivation reduced soil quality for both sites, as differences in management-dependent properties resulted from land use within map units. Management-dependent properties such as soil organic carbon, total nitrogen, particulate organic matter, and mineralizable carbon were most sensitive to land use changes.; Our second study used management-dependent soil properties to estimate near-surface soil hydraulic properties through the development of pedotransfer functions. This was done to improve interpretations within map units. Multiple regression analysis was used to relate management-dependent properties including bulk density, water dispersible clay, water stable aggregates, and soil strength to soil hydraulic properties such as infiltration rate, saturated hydraulic conductivity, and soil water content at field capacity and permanent wilting point. These models estimated infiltration rate with reasonable accuracy, while saturated hydraulic conductivity, soil water content at field capacity and permanent wilting point were estimated with slightly less accuracy.; In our third study, soil solution-mineral stability relationships as impacted by land use were assessed using thermodynamics. Soil solutions were extracted using centrifugation, concentrations were measured, ion activities were calculated, and stability diagrams were developed. Differences in ion concentrations in solutions existed as a function of management. Stability diagrams suggested croplands to favor hydroxyl-interlayered vermiculite, while hayland system tended to shift towards the hydroxyl-interlayered vermiculite favoring kaolinite as a metastable phase. Differences in stability were controlled by pH rather than differences in soluble Si and Al concentrations.