Soil Carbon Sequestration in Ponds of Gordon Euryale Seed in the Pear River Delta

Soil is the largest carbon pool in terrestrial ecosystems, and maintaining or increasing soil organic carbon (SOC) storage helps mitigate climate change. This study investigated the potential of SOC storage in agricultural ponds, a common land use type in the Pear River Delta. Ponds for producing Gordon Euryale Seed for medical and healthcare purposes were selected to assess the impact of planting years on SOC storage. Soil samples were taken from ponds with 0, 24, and 60 years of production history for separating soil aggregates of various sizes by wet sieving, assessing their stabilities, and determining their carbon and nitrogen contents. Compared with the control (a pond without Gordon Euryale Seed), soil aggregates of > 0.25 mm decreased by 36.94 and 52.63% after 24 and 60 years of planting Gordon Euryale Seed, respectively. Conversely, soil aggregates > 0.25 mm increased by 58.54% and 67.89%. Meanwhile, mean-weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates > 0.25 mm (R0.25) increased, and fractal dimension (D) decreased, suggesting soil aggregates became larger and more stable as planting years grew. As a result, SOC storage increased with planting years, as did the relative contribution of larger soil aggregates (>0.25 mm) to SOC. The outcomes of this work suggest that planting Gordon Euryale Seed is a land use with good economic return and carbon sequestration benefit.