You are currently viewing The Effect of Humic Substances on Rock Phosphates
Humic acid

The Effect of Humic Substances on Rock Phosphates

The ability of humic substances to solubilize and complex with natural minerals, such as rock phosphates, is well documented. The bioavailability of nutrients released from rock minerals by microbiological activity is enhanced in the presence of humic substances.

Humic substances can improve the effectiveness of rock phosphates by causing the release of (PO4)3- anions and (Ca)2+ cations from hardly-soluble rock minerals because of high total acidity, ability to complex and chelate the resulting solutions and stimulate microbial metabolism.

Natural Leonardite or oxidized lignite is a complex super mixture of high and low molecular weight humic substances. The lower molecular weight constituents (fulvic acid) are primarily responsible for the solubilization of phosphate minerals. Just like the fulvic acid fractions, the higher molecular weight components (humic acid) also engage in solubilizing minerals, have a high capacity for stimulating biological activity and greater potential for chelation. In natural soil system, the two components may act synergistically by complementing each other.

Humic substances also chelate iron, zinc, copper and complex with many other trace elements. Elements typically found in natural phosphate minerals, such as zinc and copper, are known to suppress pathogens and encourage the growth of beneficial organisms.

These phenomena have environmental implications as well because the solubilization of rock phosphates by humic substances can reduce the need for industrial acidification of rock phosphate used for the production of phosphatic fertilizers. Industrial production of phosphate fertilizers is extremely inefficient and creates enormous waste piles that are burdened with contaminants. Additionally, 60 to 80% of all highly soluble phosphate fertilizer applied to soils is lost to the environment.

Colloidal humic substances are part of natural soils and help retain nutrients in the soil system through soil stabilization and rare earth elements.