Soil carbon losses by water erosion: Experimentation and modeling at field and national scales in the UK

Ten years of erosion data from the Woburn Erosion Reference Experiment, Bedfordshire, United Kingdom, show that the total amount of carbon removed as particulate organic matter from individual plots ranged from 76 to 312 kg ha−1. In general, losses were less from minimally tilled plots cultivated across the slope than from plots given standard cultivations up and down the slope. Losses of carbon by erosion accounted for 2–50% of soil carbon change. Using a sediment delivery model combined with carbon enrichment data from this study and previous literature, we calculate that the amount of carbon mobilized by erosion in England and Wales is between 0.2 and 0.76 Tg C y−1, of which 0.12–0.46 Tg C y−1 is delivered to surface waters. If the eroded soil carbon were completely replaced and the eroded material protected from decomposition in sediments, then there is a potential sink on eroding cropland in the UK of up to 0.75 Tg C y−1, which represents a significant uncertainty in the terrestrial carbon budget.