Potassium release from K-bearing minerals treated with organic acids under laboratory conditions

Abstract

Potassium (K)-bearing minerals are vital for soil fertility and act as slow-release reservoirs for plant nutrients. Organic acids, such as oxalic and citric acids, enhance K dissolution. Time-dependent experiments measured K dissolution from minerals in oxalic and citric acids. Potassium Incubation period (time) was assessed by dissolving K-bearing mineral residues in organic acid solutions (oxalic and citric acids), and total K content was determined by flame photometry following acid digestion. Oxalic acid enhanced K release by 25% more than citric acid. For biotite-mica, increasing oxalic acid concentration from 0.5 to 5.0 mmol/L raised K release from 800 to 1600 mg/kg. During a further increase to 10 mmol/L, slightly improved dissolution. Percentage K release varied by mineral type, biotite-mica, muscovite-mica, and K-feldspar recorded 5–11%, 3–7%, and 2–6% respectively. Citric acid caused significant K release between 0.5 and 1.0 mmol/L, with increases up to 10 mmol/L. Above 5 mmol/ L, muscovite-mica dissolved more K than biotite-mica and K-feldspar, with K-feldspar showing higher dissolution percentages of 3.1–7.5% in citric acid than oxalic acid that recorded 2.4–6.2%. Organic acids enhance K release via chelation, destabilization of mineral surfaces, and solubility increases. Oxalic acid’s superior performance highlights its role in improving soil fertility. Also, oxalic acid outperformed citric acid in dissolving K from minerals, underscoring the importance of targeted nutrient management strategies.