A Preliminary Investigation of Sorption and Mobility of Phosphate in a Danish Spodosol

Abstract

Abstract A preliminary comparative phosphate sorption and mobility study of two almost identical Danish spodosols, a fertilized soil having received ≍ 1030 kg P/ha over 45 years and a non-fertilized soil, showed no indication of increased phosphate leaching out of the profile from the fertilized soil compared to the non-fertilized soil. The Langmuir sorption capacity (Pmax) determined on air-dried samples could be accounted for by the aluminium and iron oxides, but Pmax corresponds to phosphate concentrations too high for the aquatic environment. However, estimates indicate that phosphate loadings up to ≍ 0.1 Pmax in Bh and Bhs horizons and up to ≍ 0.3 Pmax in Bs and C horizons (so-called critical phosphate loads) can be tolerated.