RETENTION OF SOLUTES BY CLAYEY COASTAL-PLAIN SOILS

A study was conducted to determine solute retention and movement rates under bare soil conditions on two clayey coastal plain soils, Faceville sandy loam and Greenville sandy clay loam. Both soils have high clay contents in the subsoil, but the Faceville is sandier at the surface. Nitrate (NO3-N) and bromide (Br) sources were applied at the rate of 125 kg/ha. Replicate samples were taken over time by depth from each soil and analyzed for NO3-N and Br. Under natural rainfall, 45 to 95 percent of these highly soluble chemicals were retained in the top meter of soil nine months after application. After one and a half years the solutes had moved to a depth of about one meter. The study showed that agrichemicals were retained for an extended period of time in the top meter of these clayey soils. High background NO3-N levels found in the Faceville soil indicated that an N buildup may occur in the root zone of clayey coastal plain soils under commonly used N application rates.