Characterization of elemental ratios and oxidative ratio of horticultural peat

Peatlands occupy 20% of the land area of Ireland and store over half of soil carbon stocks. Over 80% of these peatlands have been disturbed by human activity such as drainage for peat extraction, afforestation and agriculture. In this study, peat samples were collected from 12 horticultural peat extraction sites in the Irish midlands. The carbon (C), nitrogen (N), hydrogen and sulphur content were determined, and from these, the carbon oxidation state (C_ox) and oxidative ratio (OR) were calculated. The carbon oxidation ratio reflects organic matter synthesis and degradation, and is thus an important parameter in understanding terrestrial carbon cycling, whilst OR represents the molar ratio of oxygen (O₂) and carbon dioxide (CO₂) fluxes associated with net ecosystem exchange. Elemental concentrations and ratios were typical for Irish horticultural peat (e.g. carbon concentrations 54%–57%), though showed site to site variability. C_ox and OR values varied between −0.22 and −0.11, and 1.04 and 1.07, respectively, and were comparable to United Kingdom peat soils. All values for OR were lower than 1.1, the value commonly used in global CO₂ partitioning studies. Further research should investigate OR values in peatland which has not been studied to date. Across all sites, measures of increased decomposition (i.e. C/N ratios) significantly correlated with increasing OR reflecting more reduced organic matter. This study provides data in temperate peat soils that increases the coverage of C_ox and OR values and will inform global CO₂ partitioning studies.