Long-term affects of a single P fertilization on Hedley P pools in a South Carolina loblolly pine plantationThis article is part of a larger document. View the larger document here.
While phosphorus (P) fertilization increases plant available or “labile” P immediately after fertilization, it is uncertain how it influences P pools over the long term in forest soils. Phosphorus pools from a 22-year-old loblolly pine (Pinus taeda L.) fertilization study were quantified using the Hedley sequential fractionation procedure, Mehlich-1, and Mehlich-3 soil tests. The Hedley fractionation procedure partitions the extracted P into six fractions, which are then defined as labile, moderately labile, and recalcitrant P pools. After 22 years, fertilization effects were limited to the surface horizon. The largest response to fertilization in this study was an increase in the Hedley recalcitrant P pools in the 0 to 10 cm soil horizon. Mehlich-3 extractable P was significantly (p = 0.02) larger in the 0 to 10 cm soil horizon of the fertilized treatment compared to the control. Our results suggest the largest portion of applied P has remained in the surface soil horizon and has the potential to increase site quality.