Impact of different chloride salts and their concentrations on nitrification and trace gas emissions from a sandy soil under a controlled environment
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.