Thursday, November 16, 2006 - 11:00 AM
324-4
Long-Term Effects of P Fertilization and Silvicultural Treatments on P Pools and Labile P in Loblolly Pine Plantation Soils.
Phosphorus (P) is one of the most limiting nutrients in forest soils. Phosphorus fertilization increases plant available or “labile” P after fertilization; however it is uncertain how P fertilization influences organic and inorganic P pools over the long term in forest soils. Site specific properties such as above- and belowground biota, soil organic matter, and mineralogy can have large influences on P availability. The goal of this project is to determine how site preparation, vegetation control, and fertilization affect P pools twenty years after fertilization at four sites in the southeastern US. Stratified soil samples were collected down one meter deep in P. taeda plantations established on well- and poorly drained sandy and clay soils subjected to low and high intensity site preparation. Phosphorus pools were quantified using the Hedley sequential fractionation procedure, Mehlich-1, and Mehlich-3 soil tests. The Hedley fractionation procedure delineates the total soil P into inorganic and organic pools; labile P, moderately labile P, recalcitrant P, and total P pools. Total soil C was measured using a LECO CR-12 carbon system. Soil C content significantly increased in the fertilized sites. Mehlich-3 P was significantly higher in the fertilized sites compared to control sites. Fertilization increased the Hedley total P and moderately labile inorganic and organic P regardless of site preparation intensity and drainage class compared to unfertilized soils. Organic P pools decreased with depth from the soil surface. After twenty years, labile P pools remained significantly higher in fertilized plots compared to controls in sandy coastal plains soils. The labile P pools in the fertilized plots increased but were smaller on the well drained sites. Results from this research will help our understanding on the long-term affects of forest fertilization prescriptions on P pools.
Recorded presentation