Extraction of Humic and Fulvic Acids from Leonardite for Agricultural Biostimulant Applications. Engineering and Sustainability Journal, [S. l.], v. 1, n. 1, p. e006, 2026. Disponível em: https://angola-journals.com/index.php/esj/article/view/24. Acesso em: 4 jul. 2026.