Factors limiting the grain protein content of organic winter wheat in south-eastern France: a mixed-model approach Marion Casagrande, Christophe David, Muriel Valantin-Morison, David Makowski and Marie-Hélène JeuffroyAgron. Sustain. Dev., 29 4 (2009) 565-574DOI: https://doi.org/10.1051/agro/2009015