title: Nanometer-scale structure of alkali-soluble bio-macromolecules of maize plant residues explains their recalcitrance in soil.
abstract: The quantity and quality of plant litter in the soil play an important role in the soil organic matter balance. Besides other pedo-climatic aspects, the content of recalcitrant molecules of plant residues and their chemical composition play a major role in the preservation of plant residues. In this study, we report that intrinsically resistant alkali-soluble bio-macromolecules extracted from maize plant (plant-humic acid) (plant-HA) contribute directly to the soil organic matter (OM) by its addition and conservation in the soil. Furthermore, we also observed that a high syringyl/guaiacyl (S/G) ratio in the lignin residues comprising the plant tissue, which modifies the microscopic structure of the alkali-soluble plant biopolymers, enhances their recalcitrance because of lower accessibility of molecules to degrading enzymes. These results are in agreement with a recent study, which showed that the humic substance of soil consists of a mixture of identifiable biopolymers obtained directly from plant tissues that are added annually by maize plant residues.
authors.affiliation: Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy. fabrizio.adani@unimi.it
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Adani
authors.forename: Silvia
authors.initials: S
authors.lastname: Salati
authors.forename: Manuela
authors.initials: M
authors.lastname: Spagnol
authors.forename: Fulvia
authors.initials: F
authors.lastname: Tambone
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Genevini
authors.forename: Roberto
authors.initials: R
authors.lastname: Pilu
authors.forename: Klaas G J
authors.initials: KG
authors.lastname: Nierop