Other soil testing methodsSeveral other tests were developed for the same purpose: to predict if additional P is needed for optimum economic yields. The most commonly used tests are the Mehlich-3 soil test, the Bray-1 and the Olson P tests. These three tests use a very different chemical extraction solution. The Mehlich-3 extraction solution is an unbuffered solution of acetate, ammonium nitrate, ammonium fluoride, nitric
acid, and ethylenediaminetetraacetic acid (EDTA). The Bray-1 solution is an unbuffered
dilute HCl andammonium fluoride solution. The procedures for the Mehlich-3 and Bray-
1 extractions call for a 1:10 soil to solution ratio and 5 minutes of shaking time. The Olsen
procedure contains sodium bicarbonate and was specifically developed for calcareous soils.