P content of mineral-poor sandy soils is steadily decreasing due to leaching caused by acidification. Sod-cutting as a traditional restoration measure for heathland vegetation increases P limitation, as most P is fixed in the top soil. To test experimentally whether soil fauna is indeed limited by P, we set up an experiment in sod-cut heathland in which we added P and/or Ca in a factorial experiment. After 3 growing seasons, we found a significant increase in herbivores and predators, with herbivore numbers higher in the P+/Ca-plots than in the P+/Ca + plots, indicating a lower availability of P in the presence of added Ca. P addition induced also an allometric effect, with medium-sized species increasing in greater numbers than both larger and smaller species.