Management-Dependent Soil Property Variability of Southeastern U.S. Coastal Plain Plinthic Kandiudults.

The National Cooperative Soil Survey (NCSS) defines a management or use-dependent property as a type of dynamic soil property which changes on a human time-scale due to anthropogenic disturbances (indicative of soil change).  Interest in soil change and C sequestration has led to increased emphasis on the characterization and inventory of these properties.  For a prime farmland map unit in the Alabama Coastal Plain, our objectives were to: 1) assess the degree of management-dependent versus use-invariant property variability, and 2) develop improved relationships between management-dependent properties and near-surface soil hydraulic properties, as these properties are fundamental to interpretations and agroecosystem function.  Near-surface (0-50 cm) soil physical, chemical and hydraulic properties within Dothan (Fine-loamy, kaolinitic, thermic Plinthic Kandiudults) consociations were measured under long-term (> 10 years) conventional and conservation row cropping systems, pasture, and forest management.  Pedon description and characterization were conducted at each site to quantify use-invariant variability. Control section sand and silt content, pH, CEC (on a clay basis)  and depth to moderate grades of soil structure exhibited low variability (%CV < 15) while control section clay content and depth to argillic horizon, ≥ 5% plinthite, and iron depletions with chroma ≤ 3 demonstrated moderate variability (15 < %CV < 35). Use –dependent properties, including soil organic C (0-50 cm) and saturated hydraulic conductivity (Ksat), displayed greater variability (%CV > 35).  Significant correlation (α=0.05) among hydraulic, management-dependent and use-invariant soil properties was observed.  Pedotransfer functions were developed using both use-invariant and use-dependent properties to estimate hydraulic properties. For these Plinthic Kandiudults, use-dependent properties (e.g. bulk density and carbon pools) accounted for soil hydraulic property (e.g. Ksat) variability more so than use-invariant properties.