Kasno, Antonius, Diah Setyorini, and Sutisni Dwiningsih. 2008. “Solubility of Rock Phosphate and Its Effect to the Growth and Yield of Maize on Ultisols”. JOURNAL OF TROPICAL SOILS 13 (1):11-22. https://doi.org/10.5400/jts.2008.v13i1.11-22.