Heteromolecular metal-humic organic complexes of the type: (A)n-(Metal)x-(B)m where A is one or several humic complexes which may be totally or partially sulfonated or may have been treated with an amine in order to protect the carboxylic groups from interacting with polyvalent cations, and B is a non-humic complexing (organic chelating agent) compound, the biological and chemical stability whereof allows for protection of the metal and the multitoothed molecule involved in the complex against degradation phenomena, both chemical and microbiological, having the beneficial effect of humic acid, as an effective plant growth and nutrition stimulant and as a metabolic and immune system activator in animals and humans.