For the initialization of the soil nutrient content the SWAT+ model requires the labile phosphorus (P) content of the surface layer. Measured soil P content is often not available for most of the catchment areas. However it is an important input data to analyse the nutrient retention. As the LUCAS Topsoil Survey dataset (Tóth et al., 2013, Jones et al. 2015) contains measured Olsen-P content data of about 20.000 soil samples in Europe, it can be used to derive approximate maps of soil P content for data scarce areas. This simple method can be applied to produce Olsen-P maps for any European catchments for which the LUCAS Topsoil dataset is relevant. Further required data are the harmonized version of the LUCAS Land Use / Cover Area Frame Survey (d’Andrimont et al., 2020), European agro-climate zone map (Ceglar et al., 2019) and the land use or land cover map of the target area. If national data on soil P content is available, that could be used further to or instead of the LUCAS Topsoil Survey dataset, after transforming the values into Olsen-P content. References: d’Andrimont, R., Yordanov, M., Martinez-Sanchez, L., Eiselt, B., Palmieri, A., Dominici, P., Gallego, J., Reuter, H.I., Joebges, C., Lemoine, G. & van der Velde, M. 2020. Harmonised LUCAS in-situ land cover and use database for field surveys from 2006 to 2018 in the European Union. Scientific Data, 7, 1–15. Ceglar, A., Zampieri, M., Toreti, A. & Dentener, F. 2019. Observed Northward Migration of Agro-Climate Zones in Europe Will Further Accelerate Under Climate Change. Earth’s Future, 7, 1088–1101. Jones, A, Fernandez-Ugalde, O., Scarpa, S. LUCAS 2015 Topsoil Survey. Presentation of dataset and results, EUR 30332 EN, Publications Office of the European Union: Luxembourg. 2020, ISBN 978-92-76-21080-1, doi:10.2760/616084, JRC121325 Tóth, G., Jones, A., Montanarella, L. (eds.) 2013. LUCAS Topsoil Survey. Methodology, data and results. JRC Technical Reports. Luxembourg. Publications Office of the European Union, EUR26102 – Scientific and Technical Research series – ISSN 1831-9424 (online); ISBN 978-92-79-32542-7; doi: 10.2788/97922