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This article in JEQ

  1. Vol. 35 No. 3, p. 806-814
    Received: May 9, 2005

    * Corresponding author(s): Ralph.Wright@gov.ab.ca
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Determining Phosphorus Release Rates to Runoff from Selected Alberta Soils Using Laboratory Rainfall Simulation

  1. Charles R. Wright *a,
  2. Mohamed Amranib,
  3. Muhammad A. Akbara,
  4. Danial J. Heaneyc and
  5. Douwe S. Vanderweld
  1. a Alberta Agriculture, Food and Rural Development, 206 J.G. O'Donoghue 7000-113th Street, Edmonton, AB, Canada T6H 5T6
    b Environment Canada, 105 McGill Street, 7th Floor, Montreal, QC, Canada H2Y 2E7
    c Norwest Labs, Edmonton, AB, Canada
    d City of Edmonton, Edmonton, AB, Canada


Phosphorus losses from agricultural land can cause accelerated eutrophication of surface water bodies. This study evaluated the use of soil test phosphorus (STP) levels to predict dissolved inorganic phosphorus (DIP) concentrations in runoff water from agricultural soils using laboratory rainfall simulation. The objectives of this study were to determine (i) to what extent STP concentrations can be used as a basis to predict P losses from Alberta soils and (ii) how extended rainfall simulation run times affected DIP losses. Soil samples collected from a total of 38 field sites, widely scattered throughout the southern half of Alberta, were subjected to rainfall simulation in the laboratory. The STP concentrations were determined using Miller–Axley, Norwest, Kelowna, Modified Kelowna Mehlich-III, and distilled water extraction methods. Each rainfall simulation event lasted for at least 90 min. Runoff samples were collected in time series for the duration of each simulation, during two distinct runoff intervals: (i) for the first 30 min of continuous runoff (T 30) and (ii) for 40 min during runoff equilibrium (T eq). For all the STP extractants and both runoff intervals, the relationship with DIP–flow-weighted mean concentration (FWMC) was linear and highly significant with r 2 values ranging from 0.74 to 0.96. However, the slopes of the resulting regression lines were, on average, 1.85 times greater for the T 30 runoff interval over those computed for the T eq interval. Thus experimental methodology greatly influenced regression parameters, suggesting that more work was needed to verify these relationships under natural conditions. In addition, with many of the r 2 values greater than 0.90 there would be little, if any, benefit derived by including soil properties in regression analysis.

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Copyright © 2006. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyASA, CSSA, SSSA