Gravimetric determination of soil organic matter

Studies were carried out to evaluate a gravimetric method for the determina tion of soil organic matter by the mass loss at 300 degreesC. The gravimetr ic method was compared with Walkley-Black, using several brazilian soils wi th variable chemical and physical properties. Gravimetric method was positi vely correlated with Walkley-Black method with the following linear regress ion equation: y = 3.72x + 0.29, r = 0.94. The angular coefficient 3.72 for tropical soils was greater than those reported in the literature for temper ate soils (from 1.68 to 2.13). The difference was due to greater oxidation degree of the organic matter. When compared with Walkley-Black method, grav imetric technique showed certain distinct advantages such as no environment al contamination with Cr6+ and improved laboratory safety eliminating the u se of concentrated sulfuric acid.