The nitrification of standard soil samples, measured as the amount of N NO 3 − being formed at different periods of time, by oxiammoniated biomass waste fertilizers was investigated. Oxiammoniated olive pits and almond shells were mixed with the soil and nitrification rates were studied over a 14-week period. The infrared spectra of soluble and insoluble ammoniated fractions and the oxidized raw material, were used to draw conclusions concerning the presence of functional groups in the fertilizer.