Stabilization of organic matter in soil by complexation is the link between metal cation and anion from the organic matter.
Considering the various forms of free iron in soils: are the most crystallized forms of free iron (geothite and lepidocrotite, not the Fe cristallized to silicate) available for the formation of organo-mineral associations ? Should it first by altered to Fe2+ or Fe3+ depending on the edaphic conditions (pH and redox potential) ?
And what about the amorphous forms of iron in soils ?