Combinations of soil properties, carbon inputs and climate control the saturation deficit dynamics of stable soil carbon over 17-year fertilizaiton

The soil organic carbon (SOC) saturation deficit (C-sd) of silt and clay fractions represents the potential for SOC sequestration in a stable form and can influence organic C stabilization efficiency. Little is known, however, about temporal changes of stable soil C-sd and how it is affected by soil properties, climate and C inputs. We investigated the temporal changes in the C-sd of fine fractions (< 53 mu m) and examined the factors controlling these changes at three dry-land sites with 17-year fertilizer management histories in China. The rates of change in the stable soil C-sd under manure treatments varied from -0.72 to -1.24% yr(-1) after 17 years of fertilization, indicating that stable C levels under manure treatments were significantly higher than those under other treatments. Stable soil C-sd was controlled by a combination of soil properties, temperature, and C inputs at all sites, and the higher variance of C-sd of fine fractions can be explained by the soil properties (up to 50%). Furthermore, the quantity of C inputs was the most influential variable for stable soil C-sd. These results revealed key controls on stable C sequestration potential and indicated the need to develop management strategies to promote stable C sequestration under long-term intensive fertilization.