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Globally, agricultural mineral soils can be either sources or sinks of carbon (C) depending on the land use, environmental conditions and management activities. In Latvia, land use change in cropland and grassland categories, including afforestation and deforestation, are the key sources of greenhouse gas (GHG) emissions. It is requested by the guidelines of the Intergovernmental Panel on Climate Change (IPCC) to use verified scientific methodology and scientifically proven emission factors and data sources in National GHG emission inventory reporting for they key source categories. The scope of the study is to evaluate organic carbon (Corg) stock in mineral soil in cropland and grassland in Latvia, where no land use changes were observed for at least 20 years. Remote sensing methods were applied to identify the National Forest Inventory (NFI) plots in grassland and cropland, where no land use changes have taken place since 1990. Vegetation index was used as criteria to validate land use. In total 120 plots on cropland and 120 plots on grassland were randomly selected for soil sampling, and the data on Corg stock in mineral soil from 218 plots were used in the calculation. Soil samples for physical and chemical analysis from 0-10, 10-20, 20-40 and 40-80 cm depths were collected in 2014 and 2015. The most widespread soil groups in the studied plots in cropland are Retisols (21.2%), Luvisols (20.8%) and Stagnosols (18.6%), but in grassland - Stagnosols (22.8%), Umbrisols (22.8%) and Retisols (20.6%). The mean Corg stock in soil at 0-40 cm depth in cropland is 83.0 t ha-1, in grassland - 88.6 t ha-1, but the mean Corg stock in agricultural soils at 0-40 cm depth - 85.6 t ha-1. Statistically significant difference between Corg stock in cropland and grassland was not detected. [ABSTRACT FROM AUTHOR]