A CENTURY 5 model using for estimation of soil organic matter behaviour at predicted climate change

The trends of carbon sequestration behaviour have been estimated for the most fertile soil type of Slovakia based on the prognosticated regional climate change scenario. The processes were modelled and simulated by CENTURY 5 model to provide these inputs: predicted information about quantification of carbon and nitrogen fluxes, and primary net of organic matter production. Soil conditions were represented by the soil type calcareous Haplic Chernozem (Danubian lowland), and the climatic scenario was related to the meteorological station Hurbanovo modelled for the period of 2005-2090. The dynamics of soil carbon and nitrogen was assessed using a conventional cropping system, concretely for 5-years crop rotation winter wheat-maize-oats (feed)-alfalfa-alfalfa modified into two alternatives: with fertilisation and without irrigation (ALT1), and excluding fertilisation and irrigation (ALT2). The model CENTURY 5 provides the simulation of three soil organic matter pools: the active (labile) pool (CL), the slow (sequestration) pool (CS), and the passive (resistant) pool (CP). The results of the model simulation for the conventional crop rotation predict that the supplies of active and slow SOM pools (CL, CS) do not show any statistically significant decreasing tendency in relation to the expected climate scenario. A moderately linear decreasing trend is expected with the passive SOM pool (CP), however, this decreasing tendency is not recognised during total carbon running (CTOT). I.e., in the future conventional crop-rotation farming no significant climate change impacts on total carbon sequestration will be presumed. In the case of ALT1, the model shows a gradual but very moderate decrease mainly with CS pool, and in that of ALT2 a significant decreasing trend is recognised with all SOM pools, mainly with CS pool. Amazing is the finding that in the case of non-irrigated but fertilised cropping system (in dry weather), the anticipated significant decrease in carbon sequestration was not observed, however, more drastic changes can be predicted in the non-fertilised and non-irrigated alternative. The average aboveground live carbon and belowground live carbon in both alternative cropping systems in relation to the conventional one have been compared. It was, estimated: in ATL1, that the primary net of organic matter decreased by almost 38% (aboveground live C) and by 43% (belowground live C), and in ALT2 by 43% (aboveground live C) and 45% (belowground live C), respectively. All these findings can be considered as the modelling outputs at the given input data, not as a firmly confirmed prognosis. Nevertheless, the achieved results of CENTURY 5 modelling assume that in the case of sufficient fertilisation and irrigation with well-managed cropping rotation practice under fertile soil conditions of Slovakia, no serious changes in carbon supplies in all SOM pools can be expected.