Impact of Poultry Manure Application on Phosphorus Desorption in Some Calcareous Soils

Abstract

Laboratory experiments were conducted to study the kinetics of phosphorus (P) desorption in different calcareous soils of Hamadan Province of Iran. Soils were fertilized with poultry manure at 50 ton ha–1 and incubated at 25 ± 1 °C at 15% moisture for 6 months. The release rate of P was studied by successive extraction with 0.5 M sodium bicarbonate (NaHCO3) over a period of 1–1752 h. Also, available P was determined. The results showed that available P in fertilized and unfertilized soils ranged from 13.3 to 55.1 and 10.0 to 50.1 mg kg–1, respectively. Phosphorus desorption from the fertilized and unfertilized soils began with a fast initial reaction, followed by a slow secondary reaction. The amount of P released after 1752 h in fertilized and unfertilized soils ranged from 319.2 to 623.9 and 309 to 586.7 mg kg–1, respectively. The amount of P released was significantly correlated with available P. The kinetics of cumulative P release were evaluated using the five kinetic equations. Phosphorus desorption kinetics were best described by the parabolic diffusion law, first order, and power function equations. Rate constants of these equations different in fertilized and unfertilized soils.