Change in the organic carbon content of soil in a long-term continuous non-irrigated maize crop [green manure, cover crop, fallow, soil organic matter, crop residue, France]

aquitaine aquitania carbon carbone carbono cereal crops crop residues cultivo intercalado cultivos de cereales culture intercalaire fallow systems intercropping monocultivo monoculture organic matter residuos de cosechas sistemas con barbecho soil sol suelo zea mays