Soil tillage impact on the relative contribution of dissolved, particulate and gaseous (CO₂) carbon losses during rainstorms

Although the impact of water erosion on soil carbon losses has been widely investigated, little is known about the relative contributions of dissolved, particulate and gaseous losses, a prerequisite for understanding the mechanisms of carbon (C) export from soils and designing mitigation procedures. The main objective of this study was to quantify the losses of dissolved organic and inorganic C (DOC, DIC), particulate organic C (POC) and soil CO2 from runoff microplots on tilled (T) and no-tilled (NT) soils. The study was performed in the Beauce region in central France under Luvisols using 45 and 80 mmh−1 artificial rains. At 45 mm h-1, T plots produced C erosion at an average of 1189.7 +- 114.8 mg C m-2 h-1 with 76.9% of it being POC (915.0 +- 100.0 mg C m-2 h-1), 21.7% DOC (258.3.0 +- 7.6 mg C m-2 h-1), 1.4% (16.3 +- 7.2 mg C m-2 h-1), DIC and 0.01% CO2. NT decreased total soil C losses by 95% (from 0.8 to 0.038 g C m-2 h-1) and soil C losses were as CO2 only. At 80 mm h-1, NT surprisingly increased C erosion by 40% compared to T (from 39.4 to 55.3 g C m2 h-1), with 95.5% of the C losses being POC vs 88.7% for T. These results on rainstorm-induced C fluxes from soils controlled by tillage are expected to be of future value: (1) for selecting appropriate land management that will mitigate against C losses from soils and improve soil carbon sequestration and; (2) to better understand the Global Carbon Cycle and further develop the existing models