Abstract: | Agroecosystems have a critical role in the terrestrial carbon cycling process. Soil organic carbon (SOC) in cropland is of
great importance for mitigating atmospheric carbon dioxide increases and for global food security. With an understanding of
soil carbon saturation, we analyzed the datasets from 95 global long-term agricultural experiments distributed across a vast
area spanning wide ranges of temperate, subtropical and tropical climates. We then developed a statistical model for estimating
SOC sequestration potential in cropland. The model is driven by air temperature, precipitation, soil clay content and pH,
and explains 58% of the variation in the observed soil carbon saturation (n=76). Model validation using independent data observed in China yielded a correlation coefficient R
2 of 0.74 (n=19, P<0.001). Model sensitivity analysis suggested that soils with high clay content and low pH in the cold, humid regions possess
a larger carbon sequestration potential than other soils. As a case study, we estimated the SOC sequestration potential by
applying the model in Henan Province. Model estimations suggested that carbon (C) density at the saturation state would reach
an average of 32 t C ha−1 in the top 0–20 cm soil depth. Using SOC density in the 1990s as a reference, cropland soils in Henan Province are expected
to sequester an additional 100 Tg C in the future. |