A process for the reduction of nitrogen oxides in an effluent from the combustion of a carbonaceous fuel while minimizing the production of other pollutants is presented. The process comprises introducing a nitrogen oxides reducing treatment agent comprising an ammonium salt of an organic acid having a carbon to nitrogen ratio of greater than 1:1 into an effluent according to a nitrogen oxides reducing treatment regimen under condition such that the treatment agent is operating on the high temperature or right side of its nitrogen oxides reduction versus effluent temperature curve, especially on the high temperature or right side of the curve plateau.