Long-term Changes in Grassland Soil Phosphorus with Fertilizer Application and Withdrawal.

摘要: Long-term phosphorus (P) applications can increase soil P concentrations in excess of agronomic optima, posing a risk to water quality. Once fertilization stops, however, it may take time for decline. Whereas adds orthophosphate, little is known about changes other forms during buildup and drawdown. This study examined pools (total P, Olsen Mehlich water-extractable P) determined by ³¹P-nuclear magnetic resonance spectroscopy (P-NMR) grazed grassland plots from Northern Ireland. Between 1994 1999, all received 8.3 kg ha⁻¹ yr⁻¹ with variable rates nitrogen (100–500 N yr⁻¹). From 2000 2005, 0, 20, 40, or 80 250 yr⁻¹; 2005 2010, no fertilizer was applied any plots. In pool at the highest were significantly elevated compared those but had decreased 2010. soils receiving lower than only There few P-NMR. Orthophosphate followed same trend observed pools; total organic inositol phosphates, orthophosphate monoesters diesters 2010 10 yr. For these soils, application cessation influenced inorganic more P.