SUBSURFACE WATER-MOVEMENT IN AN UPLAND COASTAL-PLAIN SOIL AS INFLUENCED BY PLINTHITE

Water movement in a Tifton loamy sand (Plinthic Paleudult) was monitored using bromide as a tracer for 86 weeks under natural rainfall conditions following treatment in late summer. Potassium bromide (KBr) was placed at depths between 10 and 43 cm and 60 and 102 cm in a soil having a 4. 4% slope. Bromide content of water from piezometers at distances up to 60 m downslope was determined at 2- 4-week intervals during the periods of perched water starting 22 weeks after the injection date. Determinations were then made for a 65-week period. Soil samples taken at depths to 4. 72 m 1 yr after treatment were analyzed for bromide content. Data from soil samples collected 1 yr after KBr treatment indicate that bromide moved slowly through the plinthic layer, was intercepted by subsurface layers of high density, and was retained in the watershed until removed by lateral flow.