Wednesday, 9 November 2005 - 2:15 PM
289-5

Changes in Phosphorus Forms in Forest Soils of the Southeast Us Twenty Years after Phosphorus Fertilization.

Bradley Miller and Thomas Fox. Virginia Tech, Department of Forestry, 228 Cheatham Hall, Blacksburb, VA 24061

Phosphorus (P) is one of the most limiting nutrients in forest soils. The concentrations of inorganic P in soil solutions are low because P is rapidly sorbed to soil colloids. Phosphorus fertilization increases plant available P after application; however it is uncertain how P fertilization influences organic and inorganic P pools over the long term in forest soils. Additionally, site preparation prescriptions can have large influences on soil properties such as soil organic matter. The goal of this project is to determine how site preparation, vegetation control, and fertilization affect P pools twenty years after application. Soil samples were collected to one meter in loblolly pine plantations established on well- and poorly drained soils subjected to low and high intensity site preparation. Phosphorus pools were quantified using the Hedley sequential fractionation procedure for noncalcareous soils. This procedure determined total P, Al-P, Fe-P, Ca-P, labile P, moderately labile P, and recalcitrant organic P pools. Fertilization increased levels of total P regardless of site preparation intensity and drainage class compared to unfertilized soils. The effects of fertilization on soil P pools will be discussed. Results from this research will help our understanding on the long-term affects of management prescriptions on P pools in pine plantations, and if future P fertilizations on these sites are desirable.

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