Title_english Distribution of soil organic carbon and nitrogen concentrations in the soil profiles (0-60 cm) at four long-term experiment sites in Sweden Summary This dataset presents the results of a soil sampling field campaign conducted at four sites in Sweden which constitute the humus balance experimental series. This series was established between 1971 and 1980 at Röbäcksdalen, Säby, Lanna, and Lönnstorp, along a climate gradient. The research objective of the study was to study the effect of cropping systems and nitrogen fertilization on soil organic carbon (SOC) and nitrogen (SON) stocks. The main outputs of this field campaign are SOC and N content at different soil depths along the profile. The file contains 560 rows (observations) and 10 columns (variables). Description of data collection "The humus balance is a long-term field experiment series established four to five decades ago (1971 and 1980) in different cropping systems at four sites (Röbäcksdalen, Säby, Lanna, and Lönnstorp). The research objective of the study was to assess the effect of cropping systems and nitrogen fertilization (N) on soil organic carbon stocks (SOC) in the full profile. The main outputs of this field campaign are SOC and N concentrations for different soil depths along the profile. Briefly, a sampling campaign was conducted at Lönnstorp (sampled in September 2015) and Lanna (sampled in September 2016) to measure SOC content along the soil profile. The first results of this campaign have been published in Börjesson et al. (2018). To obtain a complete dataset for all sites in the series, samples were collected at two other sites, Röbäcksdalen on 25th June 2019 and Säby on 26th August 2020. During the sampling campaigns at each of the four sites, soil samples were taken in the cereal monoculture where crop residues were retained, and in the ley rotation in the treatments with zero and the highest N fertilization rate. Samples were taken using an auger down to 60 cm depth. Five cores per plot were taken and sliced into nine depth layers, 0-20, 20-22.5, 22.5-25, 25-27.5, 27.5-30, 30-35, 35-40, 40-50, and 50-60 cm. The rationale for the denser sampling in the upper subsoil was to detect potential treatment effects in the transition zone between C-rich topsoil and C-poor subsoil. After drying the soil at 40 degree Celsius, carbon and nitrogen content were determined using the dry combustion method on a LECO CNS analyzer (LECO Corporation, St Joseph, MI 49085, USA) " file content The file contains 560 rows (observations) and 10 columns (variables) Temporal resolution One time point Geographic location Sweden Geographic description These long-term field experiments are located at four sites Röbäcksdalen, Säby, Lanna, and Lönnstorp that span eight degrees of latitude in Sweden Source of the data: primary data Funding agency Financial support was provided by the Swedish Research Council for Sustainable Development (FORMAS, grant 2022-00214) and by the Swedish Farmers’ Foundation for Agricultural (SLF, grant O-18-23-048). topic categories cropping systems, environment, climate Keywords soil organic carbon; subsoil; leys; plant nutrition; soil nitrogen; long term ecological research; nitrogen fertilisation; soil carbon storage Data collector Swedish University of Agricultural Sciences Responsible department/unit Department of Ecology/Ecosystem Unit Contributor(s) Thomas Kätterer, Martin A. Bolinder, Gunnar Börjesson Conct person Thomas Kätterer ; Department of Ecology, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden variable_name variable_description site_name name of the experimental and sampling site experiment_id unique identification code of the humus experiment series. R3-0020 indicates soil organic carbon and nitrogen in a cereal cropping system. R3-0021 indicates soil organic carbon and nitrogen in a ley rotatation system treatment_id This is the unique identification code of the treatment. There are two extreme treatments in the cereal rotation and two in the ley rotation rotation type of crop rotation or cropping system associated with the treatment n_rate Nitrogen fertilization rate used for each treatment [Kg N ha-1 yr-1] upper the upper boundary of the sampling soil depth [cm] lower the lower boundary of the sampling soil depth [cm] soc_conc soil organic carbon concentration [g kg-1] n_conc Nitrogen concentration [g kg-1] sampling_date sampling date or the date on which soil samples were collected. Treatment treatment_description 201 This treatment represents 0 nitrogen application in the cereal monoculture rotation 204 This treatment represents 120 Kg N ha-1 yr-1 nitrogen application in the cereal monoculture rotation A This treatment represents 0 nitrogen application in the ley rotation D This treatment represents 150 Kg N ha-1 yr-1 nitrogen application in the ley rotation Related publications Börjesson, G., Bolinder, M.A., Kirchmann, H., Kätterer, T., 2018. Organic carbon stocks in topsoil and subsoil in long-term ley and cereal monoculture rotations. Biol. Fertil. Soils 54, 549–558. https://doi.org/10.1007/s00374-018-1281-x Bukombe, B., Bolinder, M. A., Börjesson, G., Menichetti, L., Lang, R., Paustian, K., & Kätterer, T. (2026). Soil carbon accrual in ley rotations compared with cereal monoculture after four decades at four long-term experiments in Sweden. Agriculture, Ecosystems & Environment, 396, 110004. https://doi.org/10.1016/j.agee.2025.110004