Sun, Q. (2020) “Humic acids derived from Leonardite to improve enzymatic activities and bioavailability of nutrients in a calcareous soil”, International Journal of Agricultural and Biological Engineering. Beijing, China, 13(3), pp. 200–205. Available at: https://ijabe.org/index.php/ijabe/article/view/5660 (Accessed: 25 July 2026).