Infiltration Variability and Correlations with Surface Soil Properties for an Eroded Hapludult

The observed differences in crop yields found in eroded fields are expected to result, in part, from differences in the soil water regime. The objective of this study was to evaluate the spatial and temporal variation of initial infiltration on eroded, cultivated Georgeville silt loam (clayey, kaolinitic, thermic Typic Hapludult) located in the Piedmont region of North Carolina. Small infiltration rings were used to obtain in situ estimates of sorptivity at 290 locations in a 2.2-ha field on each of three dates. Antecedent soil water content, particle-size distribution, color-development equivalent, and surface curvature were also measured. Sorptivity (initial infiltration) values were lognormally distributed and positively correlated with color-development equivalent and clay content and negatively correlated with silt content. Sorptivity increased with level of erosion severity along guidelines for erosion class determination established by the National Cooperative Soil Survey. Sorptivity tended to be higher in convex regions in the field than in concave regions. Spatial-variability analysis of sorptivity measurements revealed stronger spatial dependence under dry than under wet field conditions. Overall, sorptivity measurements were too variable to be used for predictive modeling purposes. A two-dimensional sliding polynomial technique was used to smooth the sorptivity data and develop maps of their spatial distribution. The same spatial-distribution patterns for sorptivity existed for different dates, but the magnitude of the values varied and was lower for wet compared with dry antecedent soil water conditions. Results of this study indicate that lower productivity of eroded sites on Piedmont soil cannot be attributed to a decreased infiltration capacity. The research reported in this publication was funded (in part) by the North Carolina Agric. Res. Serv.