Approximating Phosphorus Release from Soils to Surface Runoff and Subsurface Drainage
- R.W. McDowell and
- A.N. Sharpley *
Phosphorus application in excess of crop needs has increased the concentration of P in surface soil and runoff and led many states to develop P-based nutrient management strategies. However, insufficient data are available relating P in surface soil, surface runoff, and subsurface drainage to develop sound guidelines. Thus, we investigated P release from the surface (0–5 cm depth) of a Denbigh silt loam from Devon, U.K. (30–160 mg kg−1 Olsen P) and Alvin, Berks, Calvin, and Watson soils from Pennsylvania (10–763 mg kg−1 Mehlich-3 P) in relation to the concentration of P in surface runoff and subsurface drainage. A change point, where the slopes of two linear relationships between water- or CaCl2–extractable soil P and soil test phosphorus (STP) (Olsen or Mehlich-3) meet, was evident for the Denbigh at 33 to 36 mg kg−1 Olsen P, and the Alvin and Berks soils at 185 to 190 mg Mehlich-3 P kg−1 Similar change points were also observed when STP was related to the P concentration of surface runoff (185 mg kg−1) and subsurface drainage (193 mg kg−1). The use of water and CaCl2 extraction of surface soil is suggested to estimate surface runoff P (r 2 of 0.92 for UK and 0.86 for PA soils) and subsurface drainage P (r 2 of 0.82 for UK and 0.88 for PA soils), and to determine a change point in STP, which may be used in support of agricultural and environmental P management.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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