The European nitrogen cycle: Commentary on Schulze et al., Global Change Biology (2010) 16, pp. 1451-1469

This paper compares data on N fluxes compiled by Schulze and colleagues, with information available in the literature and publicly available open databases, and finds important discrepancies for a number of such fluxes for Europe (emissions, deposition, aerosol formation of compounds containing N) -- exceeding a factor of two in several cases. A qualitative assessment of the uncertainties of the respective approaches indicates that these differences are beyond the uncertainty margins that can be reasonably attributed to the respective data. We conclude that the results should be used with caution, that agricultural application of N should still be considered to be the largest source of N released to the environment, and that this agricultural N affects soils more strongly than atmospheric deposition, at the European scale.