Quantifying carbon input for targeted soil organic carbon sequestration in China's croplands

Increasing the soil organic carbon (SOC) pool in croplands can not only promote crop production but also mitigate climate change. The objective of this work was to quantify the needed C input rates for both maintaining China's cropland SOC and improving it to global average level. By using a biogeophysical model (Agro-C), we performed simulations with a high spatial resolution (10 x 10 km) across China's croplands to quantify the C input rate under given scenarios. The model simulations showed that an average C input of 2.1 Mg C ha(-1) year(-1) is required to stop soil C loss and that SOC density could approach the global mean of 55 Mg C ha(-1) by 2050 when 5.1 Mg C ha(-1) year(-1) is incorporated into the soils. The quantified C inputs showed a large spatial disparity, depending on the existing SOC level, mean annual temperature and precipitation. The existing SOC level in Heilongjiang Province, where the cropland area accounts for 9.2 % of the national total, is much higher but the current C input is much lower than it is elsewhere. Increasing the organic C input should be given priority in this province.