Extraction of humic and fulvic acids from leonardite for agricultural biostimulant applications
Keywords:
Biostimulants, Leonardite, Humic substances, Humic acids, Fulvic acids, Sustainable agricultureAbstract
Biostimulants have emerged as a promising strategy to support sustainable growth in global agribusiness. Brazil, as one of the world’s leading agricultural producers, increasingly demands efficient and sustainable alternatives to enhance productivity. Among biostimulants, humic substances stand out due to their positive effects on soil properties and plant development. These compounds can be obtained from different mineral sources, and their origin influences their composition and effectiveness. Leonardite is recognized as one of the richest natural sources of humic substances and is widely used to produce agricultural biostimulants. In this study, the extraction of humic and fulvic acids from leonardite sourced was investigated, motivated by growing industrial interest in this material. The study included physicochemical characterization of the raw material and optimization of extraction conditions. A simplified sequential extraction approach was evaluated to investigate how operational parameters influence the selective recovery of humic substances. A 2² factorial design was applied to evaluate the effects of reagent concentration and extraction time. For fulvic acid extraction, the highest concentration (160.0 mg L⁻¹) was obtained at high acid concentration and short extraction time (30 min). For humic acid extraction, the maximum concentration (255.6 mg L⁻¹) was achieved under alkaline conditions after 3 h of extraction. FTIR analysis confirmed the presence of characteristic functional groups of humic substances in both the raw material and the extracted fractions. The results demonstrate that humic substances can be efficiently extracted under controlled conditions using a simple process. The short extraction times and operational simplicity highlight the potential for scale-up and industrial application, particularly in the production of agricultural biostimulants. Furthermore, the study contributes to the understanding of how extraction conditions influence the selective recovery of humic and fulvic fractions from leonardite.
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Copyright (c) 2026 Diogo F. Campos, Neli B. de Miranda, Aline G. Gehrke, Vanderleia Botton (Author)
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