The vulnerability to decomposition of organic C in Amazonian podzols as a result of predicted drier soil moisture regimes was tested: more than four times as much CO₂ was released from soils under oxic conditions with the addition of N relative to soils under the prevailing anoxic conditions. An extrapolation of the data to the whole of the Amazonian podzols suggests that this increased C-CO₂ flux to the atmosphere could be equivalent to 8 % of the current net global C flux to the atmosphere.