The effect of differentiated phosphorus-potassium fertilization on crop yields under simulated immission of sulphur and preventive liming was tested in a five-year pot experiment. The tests were carried out on two kinds of soil: brown (heavy loamy sand) and black earth (medium silty loam). An increased phosphorus-potassium fertilization applied under conditions of a considerable drop in the brown soil reaction brought about by sulphur immission, was found to attenuate depression in the crop yields. Now, at the prolonged sulphur application with a parallel treatment to maintain soil reaction at the level optimum for plants, interaction between sulphur doses and phosphorus-potassium fertilization was found positive. The above process began when the first negative symptoms of the sulphur impact on plants were noticed. In the case of brown soil, it took place in the second, and of black earth only in the last year of the experiment.