Extractable aluminium, iron and manganese in mineral soils: III Comparison of extraction methods

Authors

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

DOI: https://doi.org/10.23986/afsci.72357

Abstract

The extractability of soil Al, Fe and Mn were studied in 102 mineral soil samples. The extractants were 0.05 M oxalate (pH 2.9), 0.05 M K4P2O7 (pH 10), 0.02 M EDTA (pH 5.3) and 1 M CH3COONH4 (pH 4.8). In the group of clay and silt soils (n = 51), the Al extracted by the four extractants correlated closely; the r values ranged from 0.91*** to 0.96***; in coarser soils (n = 51) the r values ranged from 0.42* to 0.82***. In clay and silt soils, the organic carbon content and soil pH together explained 50 % of the variation in oxalate-extractable Al, 70 % of the variation in pyrophosphate-extractable Al, 53 % of the variation in pyrophosphate-extractable Fe and 56 % of the variation in acetate-extractable Al. The clay and organic carbon contents together with soil pH explained 77 % of the variation in EDTA-extractable Al in clay and silt soils. In coarse soils, the extractable metals were not closely related to the soil characteristics.