Distribution of nitrous oxide emissions from managed organic soils under different land uses estimated by the peat C/N ratio to improve national GHG inventories.

Nitrous oxide (N2O) contributes substantially to greenhouse gas (GHG) emissions in the agricultural and land-use sectors. Owing to the high effort needed for measuring N2O emissions and the resulting lack of sufficient field measurements to apply at country-wide scale, soil-borne N2O emissions are often estimated by applying published IPCC default emission factors. To examine the data reported in the national GHG inventory, the current study utilizes a large data set of soil C/N ratios to predict N2O emissions and their distribution from drained organic soils in Switzerland. Calculated emission rates increase in the order of forest<grassland<cropland, and they are similar to the mean values currently used in the inventory. Distributions of N2O emissions are highly positive-skewed and they reveal probabilities of 10 and 14% for cropland and grassland, respectively, to be above 20kg of N2O-N per hectare and year. It is likely that the greater part of N2O from drained organic soil derives from N released upon peat decomposition, and not from fertilization. In conclusion, this research shows that measurement of soil C/N ratios improves the reliability of organic soil N2O emissions estimates on a national scale and identifies site conditions where future emission measurements would be most effective for reducing the uncertainty in the GHG inventory.