The Steinach Grassland Experiment: Soil chemical properties, sward height and plant species composition in three cut alluvial meadow after decades-long fertilizer application

The Steinach Grassland Experiment (SGE) is probably the oldest still-running grassland fertilizer experiment in Continental Europe. It was established on an alluvial Alopecurus pratensis meadow in southeast Germany in 1933. The aim of this study was to provide detailed information on this experiment concerning the effects of decades-long nitrogen, phosphorus, potassium, and calcium application (46 treatments in total) on (1) soil chemical properties, (2) sward height, (3) plant species composition, and (4) species richness of vascular plants derived from a field survey in spring 2008. (1) A steep gradient of soil properties was recorded, namely plant-available (Mehlich III) P (14–161 mg kg−1), K (82–1018 mg kg−1) and Ca (532–3336 mg kg−1) concentrations, C:N ratio (6.9–10.4) and pH (H2O) (4.7–7.0). (2) Compressed sward height in the third week of May 2008 ranged from 11 cm in the control to 47 cm in the limed plot with high N, P, and K application. (3) Although fertilizer application altered the plant species composition, diversification of plant communities was not as high as in the case of fertilizer application on low productive soils in other experiments. This was caused by sufficient nutrients enabling the survival of species adapted to high nutrient availability, even in the unfertilized control. The species composition in productive alluvial grasslands is substantially less affected by fertilizer application than in low productive grasslands. (4) Long-term fertilizer application negatively affected the species richness of vascular plants directly by soil acidification and indirectly by an increase in sward height. The extent to which N application negatively affected species richness was dependent on whether N was applied alone or in combination with other nutrients and whether N application acidified the soil.