Media type: E-Article Title: 50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland Contributor: Lassaletta, Luis; Billen, Gilles; Grizzetti, Bruna; Anglade, Juliette; Garnier, Josette Published: IOP Publishing, 2014 Published in: Environmental Research Letters, 9 (2014) 10, Seite 105011 Language: Not determined DOI: 10.1088/1748-9326/9/10/105011 ISSN: 1748-9326 Origination: Footnote: Access State: Open Access