On the basis of the results of 13 year strict summer experiments on the dynamics of pH of soils which were unlimed (acidification) or limed (reacidification) on permanent grassland on two different mineral soils three phases differing in the average rate of pH change (∆pH/year) are presented. Phase III (about 10 years after liming) had the fastest changes. The rate of reacidification exceeded the reate of acidification. The increased efficiency of nitrogen compounds mineralization nitrification was accompanied by an increase in the rate of pH changes.