A Novel Method for Characterizing Geometries of Interaggregate Planar Pores In Soils with Vertic Properties.

Interaggregate planar pores in soils with vertic properties often act as preferential flow paths that affect soil water infiltration, redistribution, drainage, and solute transport. The geometries of these dynamic pores are difficult to quantify using traditional morphological descriptions.  Newer techniques such as X-ray computed tomography are able to quantify these pores but at significant costs and require sample sizes that restrict the characterization of these pores.  This study investigates the application of multistripe laser triangulation (MLT) scanning for characterizing interaggregate planar pores. MLT is a structured-light technique that sweeps a series of parallel laser stripes against an object to determine relevant information about its surface topography.  When applied to soil profiles, portions of the laser stripe get ‘lost’ between aggregates as the pattern is swept across the structured surface. The results are defects in the captured digital mesh that appear to represent actual pores in the profile surface. Our objectives were to assess the ability of MLT scanning to capture information about planar pores and to identify useful metrics for characterizing the geometry of these pores. This work was conducted in a Grundy silt loam (fine, smectitic, mesic Aquertic Argiudolls).  This soil is located in a gently-sloping prairie with a mean annual precipitation of 101 cm and a mean annual temperature of 13.6^o C.  Digital photography was used to record the actual pores, which were compared to patterns of missing data (i.e., digital pores) from MLT scans on the same core. Results, including correlations between actual and digital pores, and geometric characterization using such metrics as perimeter, area, thickness, and tortuosity, will be presented.