Extractable aluminium, iron and manganese in mineral soils: II Extractability by oxalate and pyrophosphate

Authors

• Raina Niskanen Department of Agricultural Chemistry, University of Helsinki, SF-00710 Helsinki, Finland

DOI: https://doi.org/10.23986/afsci.72356

Abstract

The extractability of aluminium, iron and manganese by 0.05 M oxalate and pyrophosphate was studied in samples of 23 mineral soils. Dilute extractants were studied because conventional reagents may cause problems in analytical work. The mean values for Al, Fe and Mn extracted by conventional Tamm’s oxalate were 67, 81 and 1.5 mmol/kg soil, respectively. On the average, 0.05 M oxalate solutions at pH 2.9 and 4.2 extracted Al, Fe and Mn amounts that were 103, 113 and 87 % and 72, 82 and 83 % of the amounts extractable by Tamm’s oxalate, respectively. Eeach metal released by 0.05 M oxalates correlated closely with that dissolved by Tamm’s oxalate; the r values ranged from 0.967*** to 0.997***. The mean values for Al, Fe and Mn extracted by 0.1 M Na4P2O7 and 0.05 M K4P2O7 were 38, 28 and 0.6 and 33, 29 and 0.6 mmol/kg soil, respectively. The amount of each metal extracted by Na4P2O7 correlated closely with that released by K4P2O7; the r values ranged from 0.87*** to 0.97***.