M. Utami, J. A. S. Akim, A. A. Ifah, and F. L. Syibyan, “Encapsulation of NPK in snake fruit peel biochar (Salacca edulis) and activated natural zeolite as a slow-release fertilizer for water spinach (Ipomoea reptans Poir)”, Sains Tanah J. Soil Sci. Agroclimatology, vol. 23, no. 1, pp. 82–91, Jun. 2026, doi: 10.20961/stjssa.v23i1.110863.