Potential carbon sequestration in a cultivated soil under different climate change scenarios: A modelling approach for evaluating promising management practices in north-east Italy

Crop productivity and soil organic carbon (SOC) turnover are strongly influenced by climatic and environmental conditions, so climate change projections are fundamental for a reliable assessment of C stock variations. Article 3.4 of the Kyoto protocol recognized cropland management as a human-induced strategy to sequester CO2 in agricultural soil, but only an evaluation of interactions with climate change can help in identifying the promising recommended management practices (RMPs) in the first commitment period and in the long term. In a long-term trial began in 1966, previously simulated with Century SOC model, we selected a specific treatment as ‘business as usual scenario’ (BU). We projected the simulations from 2008 to 2080, hypothesizing different reliable SOC sequestration practices to be compared with BU: farm manure application (FM), reduced tillage (RT) and grassland conversion (GR). For this, we used climate data from four global climate models (CMs: Had3, GCM2, CSIRO2, PCM) forced by four IPCC emission scenarios (SRES). The results clearly indicated that RMPs could affect the C balance in agroecosystems more strongly than climate change. Conversion to grassland was the most promising practice for sequestering C, allowing an average accumulation of 245 and 1377 g C m−2 at the end of the first commitment period and in 2080, respectively. Manure application (at the rate considered) was anyway a potential C sequestration option that was more effective than reduced tillage in the first commitment period, but slightly less efficient at the end of the simulation. BU was a source of C at 2080 only for the pessimistic climate model Had3, as a consequence of increasing temperature and reduced precipitation, with a depletion of −94 g C m−2 in 2080. With the other CMs, the BU always resulted in a carbon sink. Despite inherent sources of variability we discussed, simulation results demonstrated that RMPs could contribute towards achieving the Kyoto targets in northern Italy.