Kinetics of Phosphorus Adsorption in The Calcareous Soils of Kurdistan Region, Iraqi

Abstract

Abstract Phosphorus is the second macronutrient which is vital for plants normal growth. In the calcareous soils, the adsorption is the main process that controls P availability to plants. This paper reviews the P adsorption phenomenon in the calcareous soils of Iraqi Kurdistan. In this study, the P adsorption capacity of the selected soils was determined by adding 10 mL of 0, 50, 100, and 200 mg P L-1 as (KH2PO4) to 1.0 g of soil and shaken for 12, 24 and 48 hours on horizontal shaker constantly. The suspensions at each period of incubation centrifuged and filtered then 1nalysed for P which represented the equilibrium P concentration. The minimum adsorption 4.42±0.44 mg kg-1 was recorded for soil4 with 50 mg P L-1 applied solution and 12 h of incubation while the maximum adsorption 124±0.05 mg Kg-1 was recorded for soil3 with 200 mg P L-1 applied solution at 48 h of incubation. These results indicate that P adsorption increased with increasing applied amount of P and time of incubation. Results also showed that the Freundlich model was the best fitted according to the greater values of R2 which was ranged from 0.7619 to 0.9984 compared to 0.738-0.9882 for Langmuir model and 0.7171-0.9986 for Temkin model. These results also suggest that in the studied soils P adsorbed through physical adsorption rather than chemical reaction and then decrease P availability in soil.