Lateral Phosphorus Movement Through Subsoil to Tile Drains. (5020)
Authors:
B.L. Allen* - Iowa State Univ.
A.P. Mallarino - Iowa State Univ.
J.L. Baker - Iowa State Univ.
J.F. Lore - Iowa State Univ.
Abstract:
Vertical P movement through soil is well documented, and P loss from fields through subsurface tile drainage has been measured for many conditions. However little research has investigated lateral P transport through subsoil to tile lines. This field study investigated lateral P movement through 3.0 m of a typical Iowa subsoil (loam texture, pH 7.7, 2 mg/kg Olsen P) between a 1.2-m deep trench and a 1.2-m deep tile line. Once the inflow rate of water added to the trench equaled tile water outflow, a solution containing 8.7 mg/L P and 98 mg/L Br anion was added to the trench and maintained at 0.6 m below the soil surface for 25 days. Most applied Br reached the tile, as maximum Br concentrations were 83-97 mg/L across
replications. However, little P reached the tile because the maximum P
concentration was 0.035-0.13 mg/L. Soil P was measured in samples taken from subsoil (61-122 cm depth) located between the trench and the tile after allowing the trench to drain. Background P was increased only in the 0.3 m of subsoil closest to the trench wall. For example, Olsen P and Bray P were 49 and 60 mg/kg,
respectively, and both tests decreased asymptotically to a 2 mg/kg background P level. Results indicate that P-deficient loamy subsoil can greatly retard the lateral P movement from a highly concentrated solution toward tile drains, presumably by precipitation and/or adsorption.
Speaker Information: Brett Allen, Iowa State Univ., Dep. of Agronomy Iowa State University, Ames, IA 50011; Phone: 515-294-6200; E-mail: [email protected]
Session Information: Tuesday, November 2, 2004, 9:00 AM-11:00 AM Presentation Start: 9:00 AM (Poster Board Number: 1646)
Keywords: Phosphorus loss; Phosphorus leaching; Phosphorus management; Water quality