Potassium chloride (KCl) and magnesium chloride (MgCl2) can be used to reduce carbon dioxide (CO2) and nitrous oxide (N2O) emissions, but their efficacy can be strongly affected by their Cl− concentration. This study aimed to compare the behaviour of different Cl− salts and concentrations with that of a typical commercial nitrification inhibitor (3, 4-dimethylpyrazole phosphate, PIADIN). KCl, MgCl2 and PIADIN were investigated under a laboratory incubation experiment for two months. KCl and MgCl2 were applied at 0.5 and 1.0 g kg−1, while PIADIN was applied at 25 mg kg−1 soil. CO2 and N2O concentrations were analysed during the incubation period. The NH+4 and NO−3 dynamics in soil were also measured. The results showed 0.5 and 1.0 g kg−1 KCl and 0.5 g kg−1 MgCl2 decreased CO2-C emissions by 43%–46% and increased N2O-N emissions by 15%–48%, whereas 1.0 g kg−1 MgCl2 decreased CO2-C emissions by 72% and N2O-N emissions by 19%. KCl and MgCl2 retarded the decrease of the NH+4-N concentration and increase of the NO−3-N concentration. PIADIN reduced the emissions of CO2-C by 113% and N2O-N by 97% and maintained a high soil NH+4-N concentration and low NO−3-N concentration. MgCl2 addition at 1.0 g kg−1 was an effective treatment as the Mg both fertilized the soil and inhibited CO2-C and N2O-N emissions. Moreover, 1.0 g kg−1 MgCl2 could retard soil nitrification, the decrease of NH+4-N concentration and the increase of NO−3-N concentration. While PIADIN had no fertilizing value, it was a more effective nitrification inhibitor than Cl− salts
