The IPCC Guidelines for National Greenhouse Gas Inventories provide default methodologies for estimating emissions of the most important greenhouse gases at a national scale. The methodology for estimating emissions of nitrous oxide (N2O) from agriculture was revised in 1996 by an international working group. Here we summarize this new methodology and apply it to the global data. The new method aims at assessing the full nitrogen cycle and takes into account N2O formation in agricultural fields (direct emissions), animal waste management systems (AWMSs) as well as indirect emissions taking place at remote places after nitrogen is lost from the agricultural fields. Using the IPCC method, we estimated that global agricultural N2O emissions almost doubled between 1960 (3.5 Tg N2O-N) and 1994 (6.2 Tg N2O-N). Direct emissions, animal waste management systems and indirect emissions make about equal contribution to total current emissions.
Mosier, A., Kroeze, C., Nevison, C., Oenema, O., Seitzinger, S., & van Cleemput, O. (1999). An overview of the revised 1996 IPCC guidelines for national greenhouses gas inventory methodology for nitrous oxide from agriculture. Environmental Science & Policy, 2(3), 325-333. https://doi.org/10.1016/S1462-9011(99)00022-2