Supplementary data for: Global Gridded Nitrogen Indicators: Influence of Crop Maps

indicators on a global grid pose unique opportunities to quantify environmental impacts from N application simultaneously on various scales and different world regions. Such calculations require the use of maps showing the geo-spatial distribution of crop production. Although there are several crop maps in the scientific literature to choose from, the consequences of this choice for the calculation of N indicators still needs to be evaluated. In this study we analyze the differences of the results for Nitrogen Use Efficiency (NUE) and N surplus calculated on the global scale using two different crop maps (SPAM and M3). For our calculations we used publicly available statistical and literature data combined with each crop map and carefully traced the origin of the arising differences between the results. Our results showed that the regions most affected by discrepancies caused by differences in crop maps (yields and physical area) are Central Asia and the Russian Federation, Australia and Oceania and North Africa. However, we also found that the in- or exclusion of grass crops influences the results as does the aggregation of crops to categories. Considering all these differences we note that for the calculation of N indicators M3 seems to provide the more plausible results. Our analysis not only highlights the importance of isolating the critical inputs, but also allows to consistently identify important parameters connected with N use and overuse on the global scale. This dataset contains: All gridded N input and output data (provided in netCDF format and includes a description of the calculation) Gridded results of N surplus based on SPAM and M3 (provided in netCDF format and includes a description of the calculation) NUE per country (comparison of data by Leip et al., 2009, Lassaletta et al., 2014 and variations of our SPAM and M3 based calculations) N content per crop and their sources for all crops in M3 and SPAM Maps of N surplus for the SPAM based calculation and the M3 based calculation