Comparison of Iron Oxide–Impregnated Paper Strips with Other Extractants in Determining Available Soil Phosphorus

Abstract

Iron oxide–coated strips (P_i) can serve as a sink to continuously remove phosphorus (P) from solution. In this way, P extraction is analogous to the P absorption by plant roots. The objective of this study was to compare the iron oxide–coated paper strips with other chemical extraction methods to estimate the plant P availability for corn (Zea mays) growing in the greenhouse in some soils of Hamadan province of Iran. Sixteen soil samples with different physicochemical properties were analyzed for available P using Olsen, Colwell, Mehlich‐1, 0.01 M CaCl₂, AB‐DTPA, and 0.1 M HCl methods and p_i. Furthermore, the effects of two P levels (0 and 200 mg P kg⁻¹) on the plant indices (P uptake, relative yield, and plant responses) were studied in a greenhouse experiment using 10 soil samples. The results showed that the amount of extractable P decreased in the order of 0.01 M CaCl₂<AB‐DTPA<p_i<Olsen<Colwell<Mehlich‐1<0.1 M HCl. The amount of P extracted by the p_i method was significantly correlated with other extractants. The amounts of P extracted by all chemical methods were significantly correlated. The results of a pot experiment showed that the amount of P extracted by the p_i method was significantly correlated with the plant P uptake. However, the other methods were not significantly correlated with P uptake. The results of this experiment showed that p_i method was able to predict the plant availability of soil P.

Keywords:

• Available phosphorus
• corn
• extractants
• Pi

Acknowledgments

The authors thank R.G. Myers of the Kansas State University for review of this manuscript and comments.