Expected effects of climate change on the soil organic matter content related to contrasting agricultural management practices based on a crop model ensemble for locations in Czechia

The organic matter stored in soils is a major carbon pool with fundamental importance for the global atmospheric carbon balance. Its decomposition contributes not only to the emission of greenhouse gases into the atmosphere but also to the release of minerals that serve as nutrients for plants growing in these soils. SOC is an indicator of soil fertility, reflecting the influences of agricultural practices on this property. Using crop models, the amount of soil organic carbon (SOC) can be simulated under the assumption of different climate scenarios and different agricultural practices. The conventional agricultural practice in Czechia includes short crop rotations of mainly cereals and oil-seed rape, mineral fertilisation and removal of crop residues for technical and energy use. However, the conventional approach is often associated with soil degradation and constant depletion of soil carbon stocks. Based on the standard crop rotation method, we compared the conventional practice (CR1) to an alternative practice (CR2), in which more effort is made towards stabilising soil carbon stocks by including cover crops in the rotation, organic fertilizers and leaving crop residues in the field. We used an ensemble of crop models (APSIM, DAISY, DSSAT, HERMES, and MONICA) to assess the carbon loss from two typical agricultural soils (Chernozem and Cambisol) at three locations in Czechia under current and future climate conditions (RCP 8.5, as represented by five global climate models). The ensemble simulations revealed that using CR2 could lead to an average increase in the SOC content by 15.427 kg/ha for Chernozem and 12.624 kg/ha for Cambisol until 2080. With the use of CR1 the SOC values on average decreased by 34.462 kg/ha for Chernozem and 24.096 kg/ha for Cambisol until 2080. The 1990 value was taken as the SOC reference level. Furthermore, both the increase (CR2) and decrease (CR1) amounts SOC stabilised after 2050. As such, even at the cost of high levels of nitrogen fertilisation and the associated risk of nitrogen leaching (CR2), the additional carbon that can be stored in soils is limited. The differences due to the different climate models are negligible in the case of CR1, while in the case of CR2, the different climate scenarios (baseline vs. future) yielded different SOC equilibrium levels, with a lower level (by 4.400 kg/ha on average) under the RCP 8.5 scenario for both soils. The results showed that carbon can be sequestered by increasing organic inputs. The crop models predicted that CR2 could lead to a higher SOC content, which occurs at the cost of high manure application levels and increased risk of nitrogen leaching.