Correlation of Iron Oxide–Impregnated Paper Method with Selected Soil Phosphorus Tests and Alfalfa Indices

Abstract

Iron oxide–coated filter paper (P_i) can estimate labile phosphorus (P) in soil by acting as a P sink. The mechanism of P_i extraction may be more analogous to P sorption by plants than extraction with chemical extractants. The objective of this work was to compare strips of paper prepared by the Chardon method with Olsen, ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB‐DTPA), Bray 1, and Mehlich 1 methods in determining available P in alfalfa (Medicago Sativa) and surface samples of 15 soils of the Hamadan province, western Iran. A pot experiment was carried out in a randomized block design with two P levels (0 and 200 mg P kg⁻¹) and three replications. Plants were harvested in three cuttings in a period of 25 weeks and were used to measure plant‐available soil P. The following soil tests for P had increasingly higher average amounts of P: paper strips, Bray 1, Olsen, AB‐DTPA, and Mehlich 1. The P extracted by paper strips was significantly correlated with P extracted by Olsen and AB‐DTPA. In the first cutting, P uptake was not significantly correlated with the P extracted by the three methods. In the second and third cuttings, plant indices were significantly correlated with P extracted by paper strips, Olsen, and AB‐DTPA. The results of the present study showed that the strip paper method can be used to detrmine available P of the studied calcareous soils.

Keywords:

• Alfalfa
• available phosphorus
• strip paper