The nitrification in variously aged spoil-soils areas, as compared to the unmined climax area, indicated a general trend of decreasing nitrification through successional stages; being lowest in the fresh spoil material and highest in the climax stand. The amount of NH4+ N in soils in contrast to NO3- N, exhibited a consistently increasing trend from fresh to the old spoil soil, thus indicating a possible inhibition of nitrification. On the other hand, the number of nitrifying bacteria, Nitrosomonas and Nitrobacter, showed an inverse relationship with the increasing amounts of NH4+ N and a direct relationship with decreasing amounts of NO3- N. In the successional stages on spoil material, the intact vegetation inhibited the nitrification process in soils. This would increase the conservation of the N and energy. The increasing amount of NH4+ N in the soil, being positively charged, can be held on negatively charged soil particles and be utilized directly by plants in synthesizing N-containing compounds without the necessity to reduce nitrate to nitrite and then nitrite to ammonium N. The reduction reactions require considerable amounts of energy. Nitrate, being negatively charged, is easily leached if it is not picked up by plants. Ca, Mg and K were in large quantity in early stages and gradually decreased as the ecosystem developed. P amounts gradually increased with the aging ecosystem, thus preparing the soils to support the vegetation which may require larger amounts of P.