Transformation of some organic matter components in organic soils exposed to drainage


Abstract: In drained Histosols used as pastures or arable fields the muck-forming process transforms organic soil formations into muck. The rush vegetation (Caricetum acutiformis and Glycerietum maximae) covering Histosols in the organic matter accumulation stage is replaced by meadow vegetation (Molinietalia order). During sustained drainage mucks are transformed into muck-like formations that contain less than 12% organic carbon. The aim of this study was to report the changes in organic matter initiated by the muck-forming process. Soil organic matter was fractionated into humic-acid carbon, fulvic-acid carbon, and humins. The amount of carbon susceptible to oxidation with KMnO4 was also determined and, based on these results, lability, carbon pool, and management indices were calculated. Additionally, hot-water extractable carbon, corresponding to microbial biomass, was determined. The study's results show that the muck-forming process caused a decrease in organic carbon and the concentration of total nitrogen, indicating a reduction in carbon sequestration in the soils. The humin fraction was predominant in untransformed soils and was positively correlated with clay, total nitrogen, and non-oxidizable carbon. Drainage of Histosols contributed to increasing the solubility of humus compounds. The humification index, and the content of humic and fulvic acids was higher in drained soils. Humic acids and fulvic acids content was 24% and 11%-12% of organic carbon, respectively. Muck formations contained more humic acids than muck-like formations. Higher \SigmaCHCF:humins ratios were also observed in drained soils. In muck-like formations this ratio was 0.91 (11-fold higher than in reference soils). Drainage contributed to an increase in hot-water extractable carbon. Carbon indices were higher in mucks than in muck-like formations.

Keywords: Degradation of Histosols, hot water-extractable carbon, humic substances, reclamation of organic soils

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