Inhibition of soil urease activity and nitrification with some metallic cations

Abstract

Investigations to study the effects of 14 metallic cations on urease activity and nitrification rate in Hansi clay loam (Typic Ustochrepts) were undertaken at Haryana Agricultural University, Hissar, Haryana (India). The metallic cations inhibited soil urease activity, and the order of effectiveness varied when compared at 100, 500 and 1000 ppm. Increasing levels of metallic cations adversely affected the urease activity. Inhibitory effects of metallic cations at 1000 pprn decreased in order: Ag+ = Hg2+ > Cu2+ >Cd2+ > Co2+ >Ba2+ > Zn2+ > Ni2+ > Fe2+ > Cr3+ > Mn2+ > Sr2+ > Pb2+ > Al3+. Effects of Cr3+, Cu2+ and Hg2+ on nitrification were also tested. Above 80% of added N was nitrified at 21 days in the control (urea alone) and 100 ppm Cr3+ treatments, whereas addition of 500 and 1000 pprn cr2+ and 100, 500 and 1000 pprn Cu2+ delayed nitrification. A considerable amount of NH+4- remained unchanged in Hg2+ -treated soils after 28 days of incubation; these soils also contained more residual NO-2 than other treatments.