Effects of liming on oxic and anoxic N2O and CO2 production in different horizons of boreal acid sulfate soil and non-acid soil under controlled conditions

In acid sulfate (AS) soils, organic rich topsoil and subsoil horizons with highly variable acidity and moisture conditions and interconnected reactions of sulfur and nitrogen make them potential sources of greenhouse gases (GHGs). Subsoil liming can reduce the acidification of sulfidic subsoils in the field. However, the mitigation of GHG production in AS subsoils by liming, and the mechanisms involved, are still poorly known. We limed samples from different horizons of AS and non-AS soils to study the effects of liming on the N2O and CO2 production during a 56-day oxic and subsequent 72-h anoxic incubation. Liming to pH ≥ 7 decreased oxic N2O production by 97–98 % in the Ap1 horizon, 38–50 % in the Bg1 horizon, and 34–36 % in the BC horizon, but increased it by 136–208 % in the C horizon, respectively. Liming decreased anoxic N2O production by 86–94 % and 78–91 % in Ap1 and Bg1 horizons, but increased it by 100–500 % and 50–162 % in BC and C horizons, respectively. Liming decreased N2O/(N2O + N2) in anoxic denitrification in most horizons of both AS and non-AS soils. Liming significantly increased the cumulative oxic and anoxic CO2 production in AS soil, but less so in non-AS soil due to the initial high soil pH. Higher carbon and nitrogen contents in AS soil compared to non-AS soil agreed with the respectively higher cumulative oxic N2O production in all horizons, and the higher CO2 production in the subsoil horizons of all lime treatments. Overall, liming reduced the proportion of N2O in the GHGs produced in most soil horizons under oxic and anoxic conditions but reduced the total GHG production (as CO2 equivalents) only in the Ap1 horizon of both soils. The results suggest that liming of subsoils may not always effectively mitigate GHG emissions due to concurrently increased CO2 production and denitrification. [Display omitted] •Organic matter and nitrogen-rich AS soils are large sources of acidity and GHGs.•Liming decreased oxic and anoxic N2O production in most horizons in AS soil.•Higher CO2 and N2O production were found in AS soil compared with non-AS soil.•Liming reduced GHG production efficiently in topsoil but not in subsoil of AS soil.•Liming often reduced N2O/(N2 + N2O) but increased CO2 production and denitrification.