LONG-TERM EFFECTS OF HEAVY-METALS FROM COMPOSTED MUNICIPAL WASTE ON SOME ENZYME-ACTIVITIES IN A CULTIVATED SOIL

A 3-year field experiment on a calcareous Fluventic Xerochrept planted with corn (Zea mays L.) was carried out to evaluate the effects of am ending the soil with high and low rates of composted municipal waste o n soil enzyme activities (alkaline phosphomonoesterase, phosphodiester ase, arylsulphatase, dehydrogenase, and L-asparaginase). These enzyme activities all increased when compost was added at rates of up to 90 t ha-1, and the phosphatases continued to show a linear increase with c ompost rates of up to 270 t ha-1. The addition of mineral fertilizer i ncreased enzyme activities in unamended soil, and masked the stimulati ng effect of compost on the amended soils. Heavy metals did not affect soil enzyme activities up to a compost addition of at least three tim es the amount specified by Italian law.