Phosphorus partitioning in grassland and forest soils of Germany as related to land-use type, management intensity, and land use–related pH

Recent literature confirmed that P fractions in soil are controlled by land use. However, differences in intensity of the same type of land use have received less attention although management intensity plays a crucial role in determining nutrient supply in soil. The objective of our work was to assess the influence of land-use intensity (LUI) on P fractions in soil. In the “Biodiversity Exploratories”, grassland and forest sites in Germany were selected in three regions (Schorfheide-Chorin, Hainich-Dün, Schwäbische Alb). In spring 2008, we sampled topsoil of 241 experimental plots. The plots included unfertilized and fertilized meadows, pastures, and mown pastures and near-natural to intensively used forests. Land-use intensity was classified according to the extent of annual biomass removal. We used the sequential extraction method of Hedley et al. (1982) to characterize P partitioning in soil. In summary, total P (TP) concentrations in soil were lowest at Schorfheide-Chorin (62–952 mg kg–1) followed by the Hainich-Dün (230–1631 mg kg–1) and the Schwäbische Alb (205–1838 mg kg–1). Differences between grassland and forest sites were mainly attributable to pH. The pH value was the most important factor among several soil properties explaining P partitioning in soil. For grassland, at pH values ≈ 6.5, the application of lime-containing fertilizer increased P availability in soil while effects of organic or mineral P fertilizers were negligible and related to the low application rates (< 12 kg ha–1). Land-use intensity contributed up to 10% of the variation in the contribution of NaOH-Pi to TP concentrations (ANOVA, Type I). In the Schwäbische Alb grassland soils, elevated LUI resulted in low NaOH-Pi concentrations in soil which was probably caused by reduced sorption. Our findings highlight the importance of LUI as a control of P fractions in soil.