Studies on phosphorus (P) reactions over time and the role of organic matter in calcareous soils are important 8 for developing P fertilizers and manure management practices. This study was conducted to determine the 9 effects of time, soil properties and manure on Olsen- P and its chemical forms in calcareous soils. Eight soil 10 samples were treated with two levels of inorganic P (0 and 300 mg kg− 1) and two levels of manure (0 and 1%, 11 w/w). Olsen- P was determined at 2, 5, 10, 30, 60, 90 and 150 days of incubation. Phosphorus fractionated to 12 NaCl+NaOH- P, citrate bicarbonate (CB- P), citrate bicarbonate dithionate (CBD- P), acetic acid- sodium acetate 13 (OAc) and HCl (HCl– P) after 5, 30 and 150 days. Olsen- P, in P- treated soils, showed a positive correlation with 14 the NH4OAc extractable Al and active CaCO3. Increases in recovery as CBD- P revealed that Fe oxides play an 15 important role in P sorption during 0– 30 days. The relative distribution of P fractions and Olsen- P followed the 16 order of HCl– PNOAc- PNOrganic- PNCBD- PNOlsen- PNNaCl- NaOH- P. The CB- P fraction was not measurable. 17 Application of manure along with P increased the recovery of applied P and recovery as CBD- P compared with 18 the P treatment. In general, manure application had an appreciable and different impact on the chemical 19 fractions of P in calcareous soils as P from manure gradually turned into available forms over the time. 20 © 2009 Published by Elsevier B.V.

Keywords