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-Dun, Schwabische 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-Dun (230-1631 mg kg(-1)) and the Schwabische 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 approximate to 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-P-i to TP concentrations (ANOVA, Type I). In the Schwabische Alb grassland soils, elevated LUI resulted in low NaOH-P-i 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.