In 1980, a cropping system experiment was started in southern Sweden on an arable soil with a low fertility status. No inorganic fertilizers had been applied since the mid 1940xs. An organic cultivation was started and compared with a similar conventional system, both including one-year forage crops and animal manure applications. An unfertilized soil treatment with the same rotation as the conventional system was used as a reference. Soil analysis revealed that previous cultivation led to a deterioration of the lime status and depletion of plant nutrients. Particularly, contents of plant available P and K were extremely low. The fertilization principle of this experiment was to add more P and K than the amount removed by crops to increase the soil fertility status. The long-term use efficiency of P in the organic system amounted to 5% of the total P added, whereas in the conventional system approximately 100% of added P was utilized. Concerning K use efficiency, there was no distinct difference between the systems amounting to about 50% utilization. The organic rotation reduced soil pH values significantly to about 5.6, whereas in the other systems it remained around 6. The large proportion of legumes in the organic system (3 out of 6 years) strongly acidified the soil due to a high proton release from legume roots. Residual amounts of inorganic N (ammonium plus nitrate) in the soil were higher in autumn and lower in spring in the organic than in the conventional systems. In addition, concentrations of N in leaching water were higher in the organic system. These results reveal that the organic system was less efficient concerning N and P utilization.