Strongly acidic soil from a postindustrial area (S mine) was neutralized with postfloatation lime (300 t/ha) and improved by addn. of municipal sewage sludge (200 t/ha). Grass was cultivated for 2 yr and mixed wood for 6 yr. After 2, 4 and 6 yr, samples of the soil were collected and studied for contents of C, NaOH, NaOH + Na4P2O7 and H2SO4 - extractable C as well as humic substances. The recultivation resulted in an increase in contents of org. C and humic acids.