Aim: To assess the consequences of agricultural intensification since the 1950s for Central Europe's plant communities of arable plants. Location: Central Germany. Methods: We employed a semipermanent plot design to analyse changes in 392 field interiors for 10 study regions, including sandy, limestone and loamy sites between the 1950s/60s and 2009. Results: The analysis revealed a reduction in the regional species pool during the 50-year period of 23% (from 301 to 233 vascular species) and dramatic losses in plot-level diversity (from medians of 24 to 7). Median cover of spontaneously growing arable plants decreased from 30% to 3%. Losses were disproportionally larger on limestone sites while sandy sites maintained a larger fraction of the original diversity. Archaeophytes, neophytes and most Poaceae (including some aggressive weeds) showed similarly strong losses as indigenous plants. This contradicts the assumption that grasses and neophytes are generally profiting from agricultural intensification. Crop diversity decreased from 25 crop plants present in the 1950s/60s to only 16 in 2009, while crop cover generally increased. Winter cereals, oilseed rape and maize are dominant today, while all other crop types showed strong declines. Main conclusions: Vegetation change over time depended on soil substrate with once markedly different arable communities now showing more homogenized community structure. Increasing Ellenberg indicator values for nitrogen and pH point to N fertilization as a major driver of change. New conservation measures such as the establishment of field flora reserves and agri-environment schemes with less intensive land use are thus urgently needed especially on limestone substrates to bring an end to the decline of this functionally distinct and increasingly threatened component of the Central European flora.