Phosphorus movement through a coastal plain soil after a decade of intensive swine manure application

Understanding the movement of phosphorus (P) in soils receiving heavy animal waste application is important for nonpoint-source pollution control. We investigated both P accumulation in soil and movement to ground water after 10 yr of intensive swine manure application (at atypical high rates) to a Coastal Plain spray field. Mehlich 3 phosphorus (M3P) was measured in soil cores collected in 1991 (following 4 yr of manure application) and 1997 (after 10 yr of application). Additionally, dissolved phosphorus (DP) was measured in ground water wells installed around the spray field. In both 1991 and 1997, the soil cores (0 to 15 cm) contained high contents of M3P (376-435 mg P kg(-1)) indicating substantial P accumulation. After 10 Sr of manure application, soil cores at a depth of 107 cm were also high in soil M3P contents (151 mg P kg(-1)), Control soils were very low in M3P (<10 mg P kg(-1)) throughout the soil profile. Ground water DP concentrations were initially (1992-1995) very low (<40 mu g P L-1), but by late 1996, DP concentrations in a few wells had increased substantially (40-480 mu g P L-1). In contrast, ground water control wells (1994-1998) were very low in DP (<40 mu g P L-1). Thus, the studied field, which received atypical high loading rates, had detectable leaching to shallow ground water as well as substantial P accumulation.