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This article in JEQ

  1. Vol. 36 No. 5, p. 1289-1300
     
    Received: Nov 16, 2006
    Published: Sept, 2007


    * Corresponding author(s): joanne.little@gov.ab.ca
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doi:10.2134/jeq2006.0502

Relationships between Soil and Runoff Phosphorus in Small Alberta Watersheds

  1. Joanne L. Little *a,
  2. Sheilah C. Nolana,
  3. Janna P. Cassonb and
  4. Barry M. Olsonb
  1. a Alberta Agriculture and Food, Conservation and Development Branch, 206, 7000, 113 St. Edmonton, AB, T6H 5T6
    b Alberta Agriculture and Food, Irrigation Branch, 100, 5401, 1st Ave S., Lethbridge, AB T1J 4V6

Abstract

Field-scale relationships between soil test phosphorus (STP) and flow-weighted mean concentrations (FWMCs) of dissolved reactive phosphorus (DRP) and total phosphorus (TP) in runoff are essential for modeling phosphorus losses, but are lacking. The objectives of this study were (i) to determine the relationships between soil phosphorus (STP and degree of phosphorus saturation (DPS)) and runoff phosphorus (TP and DRP) from field-sized catchments under spring snowmelt and summer rainfall conditions, and (ii) to determine whether a variety of depths and spatial representations of STP improved the prediction of phosphorus losses. Runoff was monitored from eight field-scale microwatersheds (2 to 248 ha) for 3 yr. Soil test phosphorus was determined for three layers (0 to 2.5 cm, 0 to 5 cm, and 0 to 15 cm) in spring and fall and the DPS was determined for the surface layer. Average STP (0 to 15 cm) ranged from 3 to 512 mg kg−1, and DPS (0 to 2.5 cm) ranged from 5 to 91%. Seasonal FWMCs ranged from 0.01 to 7.4 mg L−1 DRP and from 0.1 to 8.0 mg L−1 TP. Strong linear relationships (r 2 = 0.87 to 0.89) were found between the site mean STP and the FWMCs of DRP and TP. The relationships had similar extraction coefficients, intercepts, and predictive power among all three soil layers. Extraction coefficients (0.013 to 0.014) were similar to those reported for other Alberta studies, but were greater than those reported for rainfall simulation studies. The curvilinear DPS relationship showed similar predictive ability to STP. The field-scale STP relationships derived from natural conditions in this study should provide the basis for modeling phosphorus in Alberta.

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Copyright © 2007. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America