Sorption Index to Estimate Phosphorus Retention Capacity in Soils

Abstract

Agricultural and livestock production systems, with significant amounts of input of phosphorus (P) to the soil, can cause losses of P to surface waters. Research in recent years has been focused on the mechanisms of P retention in different soil types, and searched indexes or parameters associated with fertilization requirements and environmental pollution. Traditionally, P reten-tion parameters have been studied by adsorption isotherms and buffer capacity estimation. Since the technique employed is complex and time consuming for routine analysis, in recent research P Sorption Index (PSI) is proposed as an alternative. This work carried out a literature review, and analyzed and discussed the techniques and calculations used by different researchers to quantify the PSI. The literature shows differences in the methodology for performing the single-point index (soil: solution ratio, amount of P added, temperature and time at the equilibrium, etc.), and in the equation to calculate the PSI. These differences have failed to standardize the methodology, making it difficult to compare results.