Preferential flow and pedotransfer functions for transport properties in sandy Kandiudults

Soils with differences in argillic and kandic horizon clay content (12-28% clay), thickness of overlying sandy eluvial horizons (ranging from <0.50 to >1.0 m), and degree of structural development occur in upland Kandiudult s oils in the Upper Coastal Plain of Georgia. Interest in agricultural site-s pecific management necessitates more adequate characterization of solute tr ansport properties between and within these Soils. Undisturbed columns (15- cm diam., n = 34) were Collected by horizon for three pedons typifying the extremes of the clay content in the argillic horizon. Breakthrough curves ( BTCs) were conducted using a Br- tracer and were evaluated by fitting the s ingle-and two-region adaption of the convection-dispersion equation (CDE) t o outflow measurements. Saturated hydraulic conductivity (K-s) measurements and methylene blue dye staining of conducting voids were also performed on the cores. Dye staining indicated differences in preferential flow occurre d between surface (Ap), eluvial (E), and argillic and kandic (Bt) horizons. Retardation factors (R) were positively correlated with clay quantities, a nd horizons possessing relatively less clay (A and E horizons) possessed th e highest alpha values (quickest solute exchange rates between mobile and i mmobile regions). Horizons with relatively higher clay quantities (Bts) had the lowest alpha and beta (ratio of mobile water to the volumetric water c ontent) values, but the highest effective dispersivity (lambda(eff)) values . Dye-stained areas were correlated (r = 0.65) with beta, which suggested b eta may be an approximation of the degree of preferential flow for these so ils. For the three: pedons studied, significant differences in alpha existe d between the extremes, and thus they are interpreted to behave differently from a solute transport standpoint. Pedotransfer functions (PTFs) were dev eloped for grossly estimating hydraulic and transport parameters.