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This article in JEQ

  1. Vol. 36 No. 4, p. 1096-1104
    Received: Mar 7, 2006

    * Corresponding author(s): bneed@umd.edu
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Spatial Variation of Soil Phosphorus within a Drainage Ditch Network

  1. Robert E. Vaughana,
  2. Brian A. Needelman *a,
  3. Peter J. A. Kleinmanb and
  4. Arthur L. Allenc
  1. a Dep. of Environmental Science and Technology, Univ. of Maryland, 1109 H.J. Patterson Hall, College Park, MD 20742
    b USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA 16802
    c Dep. of Agriculture, Univ. of Maryland Eastern Shore, Princess Anne, MD, 21853


Agricultural drainage ditches serve as P transport pathways from fields to surface waters. Little is known about the spatial variation of P at the soil-water interface within ditch networks. We quantified the spatial variation of surficial (0–5 cm) soil P within vegetated agricultural ditches on a farm in Princess Anne, MD with an approximately 30-yr history of poultry litter application. Ditch soils from 10 ditches were sampled at 10-m intervals and analyzed for acid ammonium oxalate-extractable P, Fe, Al (Pox, Feox, Alox), and pH. These variables were spatially autocorrelated. Oxalate-P (min = 135 mg kg−1, max = 6919 mg kg−1, mean = 700 mg kg−1) exhibited a high standard deviation across the study area (overall 580 mg kg−1) and within individual ditches (maximum 1383 mg kg−1). Several ditches contained distinct areas of high Pox, which were associated with either point- or nonpoint-P sources. Phosphorus was correlated with Alox or Feox within specific ditches. Across all ditches, Alox (r = 0.80; p < 0.001) was better correlated with Pox than was Feox (r = 0.44; p < 0.001). The high level of spatial variation of soil P observed in this ditch network suggests that spatially distributed sampling may be necessary to target best management practices and to model P transport and fate in ditch networks.

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