A quick field test for evaluating phosphorus movement in sandy soils

Abstract

Assessing the risk of phosphorus (P) leaching in sandy soils requires a valid and practical indicator of the depth to which applied P has moved in soil. This paper describes a rapid field test for soil P called the Phosphorus Quick Test (PQT) that is based on the phosphomolybdate blue procedure. One gram samples of soil taken from known depths within a soil profile were saturated with 0.10 M HCl on a porcelain spot plate and a few drops of the solution were treated with phosphomolybdate reagent to form a blue colour. The depth to which P has moved into the soil can be determined visually after only a few minutes. A comparison of the PQT results with soil (Mehlich-1 P) and water-soluble P tests showed that the PQT could accurately determine the depth of P movement in sandy soils. Results of the PQT at a field site that had received a single, heavy application of dairy lagoon effluent showed that considerable downward movement of P occurred in some areas of the field as a result of the effluent application. © 2005 Taylor & Francis Group, LLC.