Distribution and cultivation intensity of agricultural peat and gyttja soils in Sweden and estimation of greenhouse gas emissions from cultivated peat soils

Digitised maps of Quaternary deposits, 40K radiation data and Integrated Agricultural Control System databases (IACS) were used in a GIS analysis to estimate the distribution and land use of agricultural peat and gyttja soils in Sweden. The total area of agricultural land (cropland and pastures) in Sweden was estimated at 3,496,665 ha and 8.6% of this area (301,489 ha) was classified as agricultural peat and gyttja soils, with 202,383 ha of deep peat, 50,191 ha of shallow peat and 48,915 ha of gyttja soils. Using detailed information on crop distribution from agricultural databases, it was possible to estimate the cultivation intensity (land use) of the agricultural land. One-quarter of the agricultural area of peat soils was intensively cultivated with annual crops and the remaining area was extensively used, dominated by managed grasslands and pastures. There was great variation in cultivation intensity between areas, from 50% annual crops down to 10%. The gyttja soils were in general more intensively cultivated than the peat soils. The improved estimates of acreage and cultivation intensity of agricultural peat soils were used to calculate annual greenhouse gas emissions from subsidence data. The total carbon dioxide (CO2) emissions from Swedish agricultural peat soils in 2003 were estimated to be between 3100 Gg CO2 and 4600 Gg CO2, which is similar to or lower than previously reported values. Emissions of nitrous oxide (N2O) were estimated at 3.2 Gg N2O in 2003. Estimated combined total emissions of CO2 and N2O from agricultural peat soils in Sweden in 2003 amounted to 4000–5600 Gg CO2-equivalents, which corresponds to approximately 6–8% of the total emissions of all greenhouse gases reported by Sweden (excluding the sink for land use, land use change and forestry — LULUCF). Agricultural peat soils represent a minor fraction of the agricultural land in Sweden but still have a significant effect on total national greenhouse gas emissions.