To Till or Not to Till

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Science  02 Dec 2005:
Vol. 310, Issue 5753, pp. 1391
DOI: 10.1126/science.310.5753.1391c

Soils contain approximately twice as much carbon as either land plants or the atmosphere. Because carbon is transferred so easily and quickly between soil and the air, how human activity might affect that transfer has important implications for the atmospheric carbon dioxide budget. Approximately 1.5 billion hectares (11% of the total land area of Earth) is cultivated, making the impact of agriculture on the concentration of atmospheric carbon dioxide potentially significant. A large debate has centered on how agricultural practices—whether the soil is tilled, a practice that accelerates the erosion of organic-rich topsoil, or cultivated using no-till methods—might affect fluxes of carbon between the land and the atmosphere.

Van Oost et al. use radionuclide and soil organic carbon data to analyze the fate of sediment and soil organic carbon during erosion and deposition in agricultural uplands. They find that, contrary to earlier studies, which did not include depositional processes, agricultural uplands can experience a net gain of carbon by the formation of new soil organic carbon at eroding sites and the burial of eroded soil organic carbon below plough depth. Thus, rather than causing a net carbon loss, tillage might be an important mechanism for carbon sequestration in certain cases. — HJS

Global Biogeochem. Cycles 19, 10.1029/2005GB002471 (2005).

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