Modeling of phosphorus sorption and buffering mechanisms in selected soils of Fiji
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Mechanisms by which P is retained in the soil include precipitation and ligand exchange, lattice diffusion and anion exchange, which have a strong effect on the bioavailability and the transport potential of P. The main objective of this research was to use phosphorus buffer index (PBI) as an indicator of the P status of selected sugarcane growing soils in Fiji to reduce the risk of excessive fertilizer applications and leaching of P into the waterways, thus minimizing contamination of the environment. Soils used in this study were Inceptisols, Mollisols, Alfisols, Oxisols and Ultisols. PBI and phosphorus isotherm measurements were performed on selected soils. Pearson's correlation, performed using Statistix (Version 10) showed that PBI has a significant negative correlation with soil pH (R = -0.67, p = 0.017). The P sorption maxima obtained using the Langmuir equation ranged from 480 to 1314 mg/kg and Pmax had a moderate positive correlation with PBI (R = 0.70, p = 0.01). The isotherm data had a significant fit to the Freundlich sorption model, with R values ranging from 0.82 to 0.97.