Iron oxide impregnated filter paper (P i test): a review of its development and methodological research

Iron oxide impregnated filter paper (FeO paper) has been used to study the availability of phosphorus (P) to plants and algae, P desorption kinetics and P dynamics in the field. Since its initial development a number of differences in the method of preparation of the paper and its application have been implemented. The purpose of this article is to (i) critically review studies on the various aspects of both preparation and use of the FeO paper and (ii) to suggest a standardized procedure.