Soil organic carbon (SOC) is one of the basic parameters of soil productivity and quality. Generally soil has potential to sequestrate or release organic carbon depending on land use/management and climatic conditions. The main aim of this article is to show changes in SOC in agricultural land of Slovakia over almost the last 40 years on the basis of modelling data of SOC stock by the RothC model and unequal development of SOC stock on agro-climatic regions of Slovakia. The results received show that average SOC stock [t/ha] in Slovakia is higher on grasslands in comparison to arable land. However, total SOC pool (t) in top of 0.2 m of soil on the modelling area of agricultural Slovak land shows that a considerable part of SOC stock is located in arable land and is approximately four times greater than on grasslands because the arable land represents about 80% of the modelling area. In the first modelling period (1970-1994), the SOC stock gradually increased, but in the second modelling period (1995-2007) no significant changes in SOC stock on the arable land were observed. In the southwest part of Slovakia, increasing of SOC stock during all modelling periods was observed; however, in the northeast part a slight increase of SOC stock only in the first modelling period (1970-1994) was found and in the second modelling period (1995-2007) decrease of SOC accumulation was observed. The results of this statistical analysis show significant relationship between carbon input/SOC stock as independent variables and agro-climatic regions as dependent variable.
Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regional SOC storage dynamics. Understanding regional carbon emission and sequestration trends is, therefore, important in formulating and implementing climate change adaptation and mitigation policies. In this study, the estimation of SOC stock and regional storage dynamics in the Ondavská Vrchovina region (North-Eastern Slovakia) cropland and grassland topsoil between 1970 and 2013 was performed with the RothC model and gridded spatial data on weather, initial SOC stock and historical land cover and land use changes. Initial SOC stock in the 0.3-m topsoil layer was estimated at 38.4 t ha−1 in 1970. The 2013 simulated value was 49.2 t ha−1, and the 1993–2013 simulated SOC stock values were within the measured data range. The total SOC storage in the study area, cropland and grassland areas, was 4.21 Mt in 1970 and 5.16 Mt in 2013, and this 0.95 Mt net SOC gain was attributed to inter-conversions of cropland and grassland areas between 1970 and 2013, which caused different organic carbon inputs to the soil during the simulation period with a strong effect on SOC stock temporal dynamics.