Long-term effects of tillage practices and future climate scenarios on topsoil organic carbon stocks in Lower Austria – A modelling and long-term experiment study

Conservation agriculture, with its reduced soil disturbance and enhanced cover, has the potential to increase carbon storage in the topsoil. However, it remains unclear how various tillage practices alter topsoil organic carbon (SOC) storage in the long-term affected by climate change. This study investigates the impacts of three tillage practices, Conventional Tillage (CT), Mulch Tillage (MT), and No-Till (NT) on future SOC stocks in the topsoil (0–15 cm), considering climate change scenarios (RCP4.5 and RCP8.5) and local soil erosion effects. Therefore, we calibrated and applied the integrated terrestrial C-N-P cycle model (N14CP) to a long-term study site with a cereal-maize dominant crop rotation in Lower Austria. Our calibration (1994–1995) resulted in a RMSE of 45.3 g m⁻² and a PBIAS of 9.6%, while validation (2000–2023) resulted in a RMSE of 103.8 g m⁻² and a PBIAS of 3.9%. Long-term simulations indicate that topsoil SOC stocks tend to increase under MT by +309 g m⁻² (baseline), +233 g m⁻² (RCP4.5), and +148 g m⁻² (RCP8.5), under NT by +1145 g m⁻² (baseline), +1059 g m⁻² (RCP4.5), and +961 g m⁻² (RPC8.5), but SOC stocks may decrease under CT by −209 g m⁻² (baseline), −267 g m⁻² (RCP4.5), and −332 g m⁻² (RCP8.5) by 2100. In contrast to conventional management, our tested conservation agriculture practices (MT and NT) may both serve as viable options to mitigate climate change and erosion impacts on topsoil organic carbon in comparable agro-ecological settings.