Due to important role of phosphorus in different physiological processes, phosphorus (P) is considered as an essential nutrient element for plants and animals. The interactions between soil constituents and P are expressed by the means of sorption-desorption isotherms and sorption-desorption kinetics. Organic matter application affects sorption-desorption isotherm and kinetic parameters. There are a good number of researches carried out on the effects of organic fertilizers on the soil physico-chemical properties and plant responses, but information on cumulative and residual effects of these materials on P sorption-desorption and kinetic parameters in soils is lacking. The objectives of this work were to study the cumulative and residual effects of a chemical fertilizer and three types of organic amendment on sorption-desorption isotherms and kinetics of P in a calcareous soil. The work was carried out at Isfahan University of Technology Experimental Farm, located in Lavark, Najafabad, 40 kms south-west of Isfahan , central Iran in 1999. The soil samples were taken from 0-20 cm depth of different plots which had received different levels of urban-waste compost, sewage sludge and cow manure as organic amendments and one level of a mixture of ammonium phosphate and urea from one to five years. The samples were then analyzed for some physico-chemical properties. Also the P sorption-desorption isotherms and kinetics were determined. Different models were examined to describe the P sorption-desorption isotherms and kinetics. The results showed that the Frundlich and Ravan-Hosner models best describe the P sorption and desorptoin isotherms, respectively. The P sorption buffer indexes increased with the number of the fertilizers application years, however, the P desorption buffer indexes were affected negatively. The cow manure and the sewage sludge treatments, showed the most cumulative and the residual effects on the P sorption-desorption buffer indexes respectively. The soil organic carbon content was significantly correlated with the P sorption buffer indexes and the soil organic C as well as with the equivalent CaCO 3 of soil correlated with the P desorption buffer indexes. The power function and the Elovich models best described the sorption and desorption kinetics, respectively. The sorption rate parameters decreased with the number of application years and the organic C content of the soils. The desorption isotherms were best described by the diffusion parabulic and the power function models. The desorption rate parameters increased with the number of application years and the soil organic C content, however the equivalent CaCO 3 content decreased the P des