Effects of Trace Elements on Nitrification in Soils

Studies to evaluate the effects on nitrification of 19 trace elements showed that all these elements inhibited nitrification of NH 4 + ‐N added to soils. Results showed that the relative effectiveness of the trace elements in inhibition of nitrification depends on the soils. When the trace elements were compared to using 5 µ moles/g of soil, Ag(I), Hg(II), Cd(II), Ni(II), As(III), Cr(III), B(III), Al(III), Se(IV), and Mo(VI) were the most effective inhibitors (average inhibition >50%), and Mn(II) and Pb(II) the least effective (average inhibition <25%) inhibitors. The average inhibition by the other elements studied [Co(II), Cu(II), Sn(II), Fe(II), Zn(II), Fe(III), V(IV), and W(VI)] ranged from 33% with W(VI) to 49% with Fe(III), Silver(I), Ni(II), Co(II), Zn(II), Mn(II), Pb(II), As(III), B(III), Fe(III), As(V), Mo(VI), and W(VI) inhibited Nitrobacter , causing accumulation of NO 2 − ‐N in one of the soils used.