Comparison between Mehlich-1 and Bray-1 extractors and iron oxide collector for phosphorus availability in soil

Abstract

The efficiency of methods Mehlich-1, Bray-1 and phosphorus collector to extract phosphorus from soils was tested. Samples of three soils, Dystric Nitosols; Rhodic Fenasols; Ferric Acresol and maize (Zea mays L.) as test plant were used in a greenhouse. Soils received two doses (9.50 and 4.75 g kg^-1) of 5 organic fertilizers: 1 - sewage sludge from Curitiba - PR; 2 - sewage sludge from Maringá - PR, both limed at 30%; 3 - sewage sludge from Curitiba - PR, limed at 50%; 4 - chicken manure; 5 - bovine manure. The experiment had a control treatment test. Plants and soil samples were collected after 40 days of sowing. While phosphorus availability in the collected soils was evaluated by extractors Mehlich-1, Bray-1 and the phosphorus collector method (disks of synthetic fabric covered by iron oxide), phosphorus concentration in plants and soil solutions were determined by the classical spectrophotometric UV-Vis method. A variance analysis of results showed that the three methods predict the phosphorus absorbed by the corn plants. Bray-1 method presented less interference with the treatments and the clay content of soils.