Distribution and forms of manganese in vertisols of Serbia

Abstract

Soil samples taken from the Ap horizont of arable land and meadows at ten different localities were analyzed for different forms of manganese, including total (HF), pseudo-total (HNO3), 0.1 M HCl-extractable and diethylentriaminepentaacetic acid (DTPA)-extractable. A sequential fractional procedure was used for Mn portioning into fractions: water soluble and exchangeable Mn (I), specifically adsorbed Mn with carbonates (II), reductant releasable Mn in oxides (III), Mn bonded with organic matter (IV) and Mn structurally bonded in silicates (residual fraction) (V). Serbian vertisols have a normal Mn content, comparable with similar soils. The total (HF) and pseudototal (HNO3) Mn contents were not correlated with soil properties, whereas the humus content positively influenced the 0.1 M HCl-extractable Mn in soil (r = = 0.49). Soil pH and CaCO3 (r = 0.57 and 0.43) showed significant negative correlations with the DTPA-extractable Mn, respectively. The different extraction methods showed similar patterns of Mn content in arable and meadow soils. The sequential fractional procedure showed that reductant releasable Mn occluded in oxides of Fe and Mn was the prevailing Mn fraction in soil, however, water soluble and exchangeable Mn and Mn bonded with organic matter had significant correlations with most of the examined soil characteristics. Potential Mn toxicity in vertisols could be observed under lower pH and saturated conditions.