Influence of different agricultural practices (type of crop, form of N-fertilizer) on soil nitrous oxide emissions

 N2O emissions were periodically measured using the static chamber method over a 1-year period in a cultivated field subjected to different agricultural practices including the type of N fertilizer (NH4NO3, (NH4)2SO4, CO(NH2)2 or KNO3 and the type of crop (rapeseed and winter wheat). N2O emissions exhibited the same seasonal pattern whatever the treatment, with emissions between 1.5 and 15 g N ha–1 day–1 during the autumn, 16–56 g N ha–1 day–1 in winter after a lengthy period of freezing, 0.5–70 g N ha–1 day–1 during the spring and lower emissions during the summer. The type of crop had little impact on the level of N2O emission. These emissions were a little higher under wheat during the autumn in relation to an higher soil NO3– content, but the level of emissions was similar over a 7-month period (2163 and 2093 g N ha–1 for rape and wheat, respectively). The form of N fertilizer affected N2O emissions during the month following fertilizer application, with higher emissions in the case of NH4NO3 and (NH4)2SO4, and a different temporal pattern of emissions after CO(NH2)2 application. The proportion of applied N lost as N2O varied from 0.42% to 0.55% with the form of N applied, suggesting that controlling this agricultural factor would not be an efficient way of limiting N2O emissions under certain climatic and pedological situations.