Herviyanti, ., Teguh Budi Prasetyo, Fachri Ahmad, and . Darmawan. 2018. “The Properties of Humic Acids Extracted from Four Sources of Organic Matters and Their Ability to Bind Fe2+ at New Established Rice Field”. JOURNAL OF TROPICAL SOILS 15 (3):237-44. https://doi.org/10.5400/jts.2010.v15i3.237-244.