http://www.tandfonline.com/doi/abs/10.1080/03650340.2012.704548
Effect of mineral and organic fertilization on crop yield, nitrogen uptake, carbon and nitrogen balances, as well as soil organic carbon content and dynamics: results from 20 European long-term field experiments of the twenty-first century
Martin Körschens, Erhard Albert, Martin Armbruster, Dietmar Barkusky, Michael Baumecker, Lothar Behle-Schalk, Reiner Bischoff, Zoran Čergan†, Frank Ellmer, Friedhelm Herbst, Sandor Hoffmann, Bodo Hofmann, Tamas Kismanyoky, Jaromir Kubat, Eva Kunzova, Christina Lopez-Fando, Ines Merbach, Wolfgang Merbach, Maria Teresa Pardor, Jutta Rogasik, Jörg Ruühlmann, Heide Spiegel, Elke Schulz, Anton Tajnsek, Zoltan Toth, Hans Wegener and Wilfried Zorn
, page 7 legend: change of columns
Right is (figure below):
Dark part of column, below: Rotation 1 (1973–1976)
Brighter part of column, above: Rotation 8 (2007–2011)