Approximating Phosphorus Release from Soils to Surface Runoff and Subsurface Drainage

Abstract

ABSTRACT 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 CaCl 2 –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 CaCl 2 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.