|Mcdowell, Richard - PENN STATE UNIVERSITY|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2002
Publication Date: January 20, 2003
Citation: KLEINMAN, P.J., NEEDLEMAN, B.A., SHARPLEY, A.N., MCDOWELL, R.W. USING SOIL PROFILE DATA TO ASSESS PHOSPHORUS LEACHING POTENTIAL IN MANURED SOILS. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. 2003. V. 67. P. 215-224. Interpretive Summary: The transfer of phosphorus from agricultural lands to surface water has been implicated in eutrophication, one of the most pervasive water quality problems in the U.S. This study examines the use of soil profile data in assessing the potential for phosphorus to be transported through the soil via leaching. Many studies have used soil profile data in this fashion, but few have validated their findings with direct observations of phosphorus leaching. This study reveals some of the pitfalls in interpreting soil profile data, showing that environmentally significant concentrations of phosphorus can be leached despite limited evidence of leaching in soil profile data.
Technical Abstract: Subsurface flow through macropores can be an important pathway for P transport through soils, particularly those that are artificially drained. We sought to assess whether data from soil profile sampling provide insight into P leaching potential through evidence of P translocation. Three soils, all with histories of intensive poultry manure application, were sampled following morphological description of the profiles. Intact pedon from individual horizons were dissected to isolate clay films. Water soluble P concentrations in the upper argillic horizons were significantly higher than in lower horizons, indicating shallow translocation of P by matrix flow; however, concentrations at depth of artificial drainage (>50 cm) were too low to suggest P leaching of environmental import. Clay film samples from roughly one third of all subsoil horizons possessed oxalate P and Mehlich-3 P concentrations significantly higher than corresponding bulk ksamples, indicating transport of P along macropores. Although all P fractions were significantly higher in the deepest horizons of the three soils than in overlying argillic horizons, suggesting translocation via bypass flow, this stratification was attributed to a lithologic discontinuity rather than leaching of manure P. Leaching experiments conducted on 30- and 50-cm intact soil columns revealed that P is readily leached through these soils. While dissolved P concentrations in leachate ranged from 0.004-0.013 mg L-1 without manure application, they rose to 0.034-2.833 mg L-1 after application of poultry manure at a rate of 85 kg P ha-1. Thus, carefully interpreted soil profile data appear to provide some insight into P leaching potential.