Measurement of in situ Phosphorus Availability in Acidified Soils using Iron-Infused Resin

Abstract

ABSTRACTA hybrid anion resin was tested for in situ phosphorus (P) availability measurement in soils of two stands recovering from acidification and having different P-sorption characteristics. The phosphate (P-PO4) sorption capacity of the resin (before saturation) was 48 µmol g−1. Sorption and elution were tested under P-PO4 concentrations common in acidic soils (0–0.42 mmol l−1) either with or without the presence of sulfate (0.2 mmol l−1). The efficiency of P-PO4 sorption was independent of the sulfate and was 100 ± 0.2% (n = 56, ± SD). The P-PO4 recovery stabilized after six elution steps (each: 50 ml of 0.5 M sodium hydroxide, resin/solution 5:1). The efficiency of P-PO4 recovery was 80 ± 7% and was used to evaluate field measurements. We determined the amount of P-PO4 in the field using resin bags in three consecutive years. The results indicate that bioavailable P is negatively related to the soil ability to retain P.