INVESTIGATION OF SUITABLE DIGESTION METHODS FOR THE DETERMINATION OF TOTAL PHOSPHORUS IN SOILS

Total phosphorus in five soils with different compositions which were obtained from different places were extracted by using Na2CO3 fusion, HClO4 digestion, HClO4 + HNO3 digestion, HF + HClO4 digestion or NaOBr oxidation methods. In order to test the suitability of the HF HClO4 d igestion the results obtained by this method were compared with the ot hers above, especially the Na2CO3 fusion which is accepted as a standa rd method. The phosphorus amount found with the HF + HClO4 digestion m ethod were almost the same as the phosphorus amount by the Na2CO3 fusi on method, while the superiority in extracting phosphorus when compare d to other methods were obvious. The methods used in the study were ev aluated according to the recovery of total phosphorus, ease of applica tion and rapidity with which they were performed. Orthophosphate in th e soil extracts was determined by the molybdenum blue colour method. T he relationships between methods are examined statistically. (C) 1997 Elsevier Science B.V.