This dataset reports greenhouse gas production measurements from a laboratory incubation of sphagnum and peat sourced from a boreal peatland complex (Siikaneva Bog, Finland). Shallow peat samples were extracted in bulk with a bread knife in October 2022 from a homogeneous sphagnum lawn at three locations within several meters distance. Three soil horizons were distinguished according to the position of the water table: above (0-3 cm), fluctuating (3-7 cm) and below the water table (7-20 cm). Three spatial replicates were united per layer. Subsamples from above and below the water table were amended with solutions of NaNO3 and NH4Cl at different concentrations and incubated in 120 ml airtight glass vials in a N2 atmosphere for 365+ days to investigate the effect of nitrogen addenda on greenhouse gas production. Two matching sets of samples were incubated at 4°C and 20°C. Vial containing only untreated water or the treatment solution were kept aside the samples as blanks. The headspace gas was sampled regularly and CO2 and CH4 concentrations determined by GC-FID (Shimadzu Nexis GC-2030). This dataset contains the measured headspace concentrations as well as cumulative carbon fluxes standardized by gram soil carbon. Headspaces were flushed with Nitrogen when CO2 concentrations surpassed 10 000 ppm. Cumulative fluxes were computed from concentration changes between measurements, including an estimate of the fraction of gas dissolved in the water column at each date, and losses during sampling. Additionally, carbon and nitrogen contents are reported from material that was archived before the incubation (soliTOC cube, elementar Analysensysteme / exceed rapid maxN). From the additional portions of the same archive, water was extracted with Rhizon samplers to probe pH and electric conductivity and determine dissolved organic carbon (elementar Analysensysteme / TOC-L analyzer with TNM-1 module, Shimadzu).