EVALUATION OF AN ALUMINUM DIGESTION BLOCK FOR ROUTINE TOTAL SOIL-PHOSPHORUS DETERMINATION BY ALKALINE HYPOBROMITE OXIDATION

Total soil P was determined in six soils differing in pH, and in organic matter, total Fe, clay and sand contents. This study was undertaken to determine whether replacement of a sand bath digestion procedure by an Al-block digestion procedure affected the efficacy of an alkaline NaOBr method for determining total soil P. An Al digestion block was used for soil oxidation with NaOBr-NaOH and the results were compared with a sand bath NaOBr method and a HClO4 method. Temperature variability was very low in the digestion block (S.D. = +/- 1.4-degrees-C) when compared with the sand bath (S.D. = +/- 20.1-degrees-C). The digestion block resulted in a greater precision in total P determination when compared to the sand bath (S.D. = +/- 3.7 vs. +/- 5.6, respectively). Linear relationships were obtained with the sand bath digestion technique (R2 = 0.981) and with the HClO4 method (R2 = 0.982). Using an Al digestion block for NaOBr-NaOH oxidation of soils for total P determination allows for a simple, precise alternative to sand bath digestion and to potentially hazardous HClO4 procedures.