ArticleCOLLOIDAL IRON OXIDE TRANSPORT IN SANDY SOIL INDUCED BY EXCESSIVE PHOSPHORUS APPLICATION 1Zhang, M. K.2; He, Z. L.2 3; Calvert, D. V.3; Stoffella, P. J.3Author Information 2College of Natural Resource and Environmental Sciences, Zhejiang University, Huajiachi Campus, Hangzhou 310029, P.R. China. 3University of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center, 2199 South Rock Rd. Fort Pierce, FL 34945. 1Florida Agricultural Experiment Stations Journal Series No. R-09209 Dr. He is corresponding author. E-mail: [email protected] Received Dec. 18, 2002; accepted June 13, 2003. Soil Science: September 2003 - Volume 168 - Issue 9 - p 617-626 doi: 10.1097/01.ss.0000090802.06903.bc Buy Metrics Abstract Colloidal movement in the soil profile is of great concern because of its suspected role in facilitating transport of contaminants to groundwater. Laboratory studies were conducted to determine the effects of excessive phosphorus (P) application on the transport of colloidal iron oxides in the surface layer of a Wabasso sand (sandy, siliceous, hyperthermic alfic haplaquods). Soils were packed in columns, and the surface layer was treated with five phosphorus application rates. A total of five pore volumes of deionized water were applied to soil columns under conditions of alternating saturated and unsaturated flow, and leachates were collected and analyzed for iron (Fe) and P concentrations. Excessive P application altered characteristics of the soil and the stability of iron oxides in the soil solution and, thus, accelerated transport of colloidal iron oxides in the soil. Concentrations of Fe in the leachates, ranging from 0.1 to 33.4 mg/L, depended on the rate of P application and varied with leaching sequence. The Fe in the leachates was mainly particulate Fe, which averaged 38.0–94.1% of total Fe in the leachates. The highest concentration of Fe in the leachate generally occurred in the soils receiving P levels as high as 1- to 3-fold of maximum phosphate adsorption calculated from a Langmuir equation. Elevated Fe transport in the form of iron oxide also increased the migration of P and trace elements in particulate forms. © 2003 Lippincott Williams & Wilkins, Inc.