Biodiversity and ecosystem functioning after 60 years of fertilization: insights from the Ossekampen grassland experiment

The biodiversity-productivity relationship of four different fertilization treatments (unfertilized control, Ca, PK, and NPK) has been assessed at the Ossekampen Grassland Experiment in 2022. Thelong-term fertilization experiment was established in 1958, on a species-rich old pasture on heavy claysoil near Wageningen, the Netherlands. The long-term fertilization resulted in grassland ecosystemswith a distinct botanical composition, confirming a significant relationship between abovegroundbiomass production (productivity) and plant species richness. However, the response to the fertilization on a selection of productivity and biodiversity indicators, above and belowground, were differentbetween treatments. The NPK treatment reached highest productivity (yield, nitrogen yield and rootdensity) as well as highest belowground biodiversity for the indicators bacterial and fungal biomass. Inthe liming (Ca) treatment highest above ground biodiversity (richness in plant species, and flowering)as well as belowground biodiversity (earthworm abundance) were measured. Our findings highlight that depending on the type of fertilization, the direction and strength of the biodiversity productivity relationship is affected.