Phosphorus desorption kinetics in two calcareous soils amended with P fertilizer and organic matter

We studied the effects of poultry manure and pistachio compost with and without phosphorus fertilizer on the kinetics of phosphorus desorption in two calcareous soils of Kerman and Koohbanan farms in the southeastern of Iran. For this purpose mono potassium phosphate, at rates of 0, and 100 parts per million of phosphorus, and air-dried manure, at rates of 0 and 4% were mixed with the soils. The soils were incubated at 24-25 degrees C and near field capacity for 90 days in the greenhouse. Afterwards, the desorption of P was studied by the successive extraction with 0.5 M NaHCO3. The results of this research indicated that application of OM and fertilizer P combined increased P recovery in each of the extraction time, adding poultry manure and 100 mg phosphorus together to the soils, increased P desorption more than pistachio compost in the soils. The phosphorus desorption rate was initially rapid and then became slower until equilibrium was approached. Kinetic data were best described by power function and simple Elovich equations. Subsequent to these equations, parabolic diffusion equation was also well fitted the time-dependent P desorption data.