Untie the knot of soil organic matter chemistry enables additional differentiation among soils and their managements

Abstract

Humic Substances (HS) represent the most stable fraction of soil organic matter and it affects the soil physical-chemical and biological properties, being fundamental for its quality and fertility. The heterogeneous and complex nature of humic components represents the main difficulty against the elucidation of the structure and dynamics of soil organic matter. Our recent findings have provided significant experimental evidence supporting the model of HS as supramolecular associations of relatively small molecules held together by hydrophobic and hydrogen bonds. These results were based on a series of experiments which showed that the conformations of humic suprastructures were altered by additions of small amounts of organic acids, while those of real macropolymers were not. Mono- and di-alkanoic acids acids were found to disrupt the weak association of humic molecules, whereas such disruption was not observed for the covalently stabilized polymers. The understanding that soil organic matter is arranged in supramolecular structures comprising molecules with a mass less than 1000 Da has prompted a number of consequent Science. First of all, if the humic supramolecular structure is composed by relatively simple molecules held together by weak bonds, it implies that the single compounds can be selectively separated and quali-quanti-tatively characterized with appropriate analytical methods, such as NMR and mass spectrometry (MS). A comprehensive description of a Humeomics Science will be presented together with the strucutral identification of molecules in the supramolecular structure. The understanding of the molecular composition of HS would signify an important achievement for research in soil and soil management. Then, the supramolecular structure of loosely bound and small soil humic molecules can be stabilized by their covalent coupling under a photo-oxidative reaction catalyzed by biomimetic homogeneous and heterogeneous catalysts. The catalyzed photo-polymerization of SOM can be achieved directly in situ on agricultural soils causing an effectively significant carbon sequestration in soil. This technology can become a practical means to reduce carbon losses from soil and contribute to mitigate global changes