In the area of the Chvaletice manganese and pyrite works, the pyrite fly dust decomposing into sulfuric acid causes considerable damage to agricultural production. Sulfuric acid is also formed from the escaping sulfur dioxide. The reaction of the affected soils is extremely acid and reaches from 4.5 to 6.5 pH, and in some cases it decreases to 2.5 pH. Soil devastation spreads to distant land in the direction of the predominating winds. Damage is caused to agricultural crops which decreases yields. It was decided to ameliorate the affected soils with high doses of calcareous composts of material obtained from fish-ponds and of marl. The purpose of the experiment, the partial results of which are described, was an operational checking of the suitability of the composts for the amelioration of contaminated soils and an estimation of the doses to be applied.