Djuniwati, S., Nugroho, B. and Pulunggono, H.B. 2013. The Changes of P-fractions and Solubility of Phosphate Rock in Ultisol Treated by Organic Matter and Phosphate Rock. JOURNAL OF TROPICAL SOILS. 17, 3 (Jan. 2013), 203–210. DOI:https://doi.org/10.5400/jts.2012.v17i3.203-210.