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** plus -N added to soils. Results showed that the relative effectiveness of the trace elements in inhibition of nitrification depends on the soils. The most effective and least effective inhibitors are reported as are average inhibition rates for the elements studied.; Studies to evaluate the effects on nitrification of 19 trace elements showed that all these elements inhibited nitrification of NH4+-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 μmoles/g of soil. Ag1, Hg2, Cd2, Ni2, As3, Cr3, B3, Al3, Se4, and Mo6, were the most effective inhibitors (average inhibition >50%), and Mn2 and Pb2 the least effective (average inhibition <25%) inhibitors. The average inhibition by the other elements studied [Co2, Cu2, Sn2, Fe2, Zn2, Fe3, V4, and W6] ranged from 33% with W4 to 49% with Fe3. Silver1, Ni2, Co2, Zn2, Mn2, Pb2, As3, B3, Fe3, As5, Mo6, and W6 inhibited Nitrobacter, causing accumulation of NO2--N in one of the soils used.