11/02/2025
Will Humic Acid "RELEASE" phosphorus and Calcium? Chelation/Complexation: Humic acid can chelate (bind with) metal cations such as calcium (\(\text{Ca}^{2+}\)), iron (\(\text{Fe}^{3+}\)), and aluminum (\(\text{Al}^{3+}\)), which are the elements that typically bind with phosphorus to form insoluble, plant-unavailable compounds in the soil. By binding the cations, the humic acid prevents them from locking up the phosphorus, thus increasing the amount of soluble P in the soil solution.Physical Mechanisms: Humic acid helps improve soil structure, which can enhance phosphorus transport and diffusion in the soil toward plant roots.Stimulation of Microorganisms: Humic acid provides a carbon source for beneficial soil microbes, which in turn secrete enzymes (like acid phosphatase) and organic acids that are responsible for the mineralization (breakdown) of organic phosphorus into plant-available inorganic forms.Competition for Adsorption Sites: Humic acid can compete with phosphate ions for adsorption sites on soil particles (like clay minerals or iron oxides), resulting in the release of more soluble P into the soil solution.Root Growth Promotion: Humic acid stimulates root development and growth, allowing plants to explore a larger volume of soil and thus access more nutrients, including phosphorus. In essence, applying humic acid acts as a "helper" to unlock phosphorus that is already present in the soil in unavailable forms, rather than a direct "digestive" agent itself.