The influence of nitrate and ammonium fertilization on N2O release and CH4 uptake of a well‐drained topsoil demonstrated by a soil microcosm experiment

The effects of the application of KNO3 and NH4Cl (100 kg N ha−1) on N2O release and CH4 uptake by a well‐aerated topsoil (porosity: 55%, water‐filled pore space: 67% of the total pore space) were studied in a laboratory incubation experiment over 50 days using a soil microcosm system with an automated registration of N2O and CH4 fluxes. The total N2O‐N losses over 50 days were low for all treatments and amounted to 0.9 mg m−2 for the control, 1.2 mg m−2 for the soil columns fertilized with KNO3, and 7.3 mg m−2 for the soil columns fertilized with NH4Cl. The slightly elevated N2O release after the application Of NH4Cl was associated with the nitrification of NH4+ added. Only −0.06% of the fertilized NH4−N was lost as N2O. This nitrogen fertilization reduced the CH4 uptake of the soil columns by 43% (NH4Cl) and 21% (KNO3), respectively.