Re‐evaluating the biophysical and technologically attainable potential of topsoil carbon sequestration in <scp>C</scp> hina's cropland

Abstract To assess the topsoil carbon sequestration potential ( CSP ) of C hina's cropland, two different estimates were made: (i) a biophysical potential ( BP ) using a saturation limit approach based on soil organic carbon ( SOC ) accumulation dynamics and a storage restoration approach from the cultivation‐induced SOC loss, and (ii) a technically attainable potential ( TAP ) with a scenario estimation approach using SOC increases under best management practices ( BMPs ) in agriculture. Thus, the BP is projected to be the gap in recent SOC storage to either the saturation capacity or to the SOC storage of uncultivated soil, while the TAP is the overall increase over the current SOC storage that could be achieved with the extension of BMPs . The recent mean SOC density of C hina's cropland was estimated to be 36.44 t/ha, with a BP estimate of 2.21 Pg C by a saturation approach and 2.95 Pg C by the storage restoration method. An overall TAP of 0.62 Pg C and 0.98 Pg C was predicted for conservation tillage plus straw return and recommended fertilizer applications, respectively. This TAP is comparable to 40–60% of total CO 2 emissions from C hinese energy production in 2007. Therefore, carbon sequestration in C hina's cropland is recommended for enhancing C hina's mitigation capacity for climate change. However, priority should be given to the vast dry cropland areas of C hina, as the CSP of C hina is based predominantly on the dry cropland.