Improved methods and apparatus (10, 74) for the solubilization of initially solid humic acids include a large-volume mixing/agitation tank (12, 76) for water and solid humic acids, together a recirculation assembly (14, 78) for continuously recirculating the water/humic acids mixture while reducing the size of the humic acids. Properly used, the apparatus (10, 74) is capable of providing relatively stable, solubilized humic acid solutions or dispersions.