Publisher Summary This chapter describes the enzymology of technogenic soils on exhausted gravel quarries. Petrov et al. conducted recultivation experiments on the exhausted gravel quarry located in a large plain near the city of Vilnius and described the results obtained in the 1986–1991 period. In 1986, the physico-chemical analyses showed that the pH was slightly alkaline in soils of group I, nearly neutral in soils of group II, and slightly acid in soils of group III. In the spring of 1987, a part of the experimental plots of each soil group was seeded with a perennial legume–grass mixture. The other part of plots received a perennial grass–legume mixture. Both mineral and organic fertilization had beneficial effects on physico-chemical and biological properties of soils, especially in their 0–10 cm layer. The pH in slightly alkaline and nearly neutral soils changed to a little extent, whereas in the slightly acid soils, it increased up to 6.8–7.1.