MORPHOLOGIC AND HYDRAULIC-PROPERTIES OF SOILS WITH WATER RESTRICTIVE HORIZONS IN THE GEORGIA COASTAL-PLAIN

Hydraulic and morphological properties of soils from a 0.36-ha site in the Georgia Coastal Plain were evaluated. Objectives included charact erizing the morphological and hydraulic properties of major horizons i n soils with plinthite, determining the extent of preferential flow, a nd relating flow/transport parameters derived from breakthrough curve analyses to morphological properties. These soils have developed from Miocene aged sediments and are classified in fine-loamy, siliceous, th ermic families of Plinthaquic, Aquic, Arenic Plinthic, Plinthic, and T ypic Kandiudults. Morphological evidence indicates that BC horizons ar e restrictive to vertical percolation of drainage water. Methylene blu e dye staining, K-sat and breakthrough curves (analyzed by two region/ MIM using CXTFIT) were measured on 15-cm-diameter undisturbed cores to determine the effects of argillic horizons, argillic horizons with pl inthite, and subjacent BC horizons on hydraulic properties of the soil s. K-sat for seven sampled pedons averaged 1.6 x 10(-2), 1.1. x 10(-2) , and 3.8 x 10(-3) mm s(-1) for Bt, Btv, and BC horizons, respectively . Dye staining and model output (MIM) indicate a greater degree of pre ferential flow with depth and subsequent less mobile area contributing to water flow. Analyses of the flowpaths indicate water is translocat ed in regions with relatively higher porosity that also contain a high er proportion of coarser pores. Micrographs indicate that flowpaths ar e associated with bio-pores and areas of better aggregation in the Pt horizons and structural voids in the BC horizons. BC horizons in these soils are less permeable because of increased clay content, differenc es in pore characteristics, and less cross-sectional area contributing to flow.