Soil surface properties control the stabilization of organic matter in the raised-bed soils of tidal swamplands

Abstract

Stabilization of organic carbon (OC) in raised-bed soils of tidal swamplands reduces greenhouse gas emissions and increases soil OC contents. However, factors controlling OC stabilization in the raised-bed soils of tidal swamplands remain unclear. Relationship between OC contents of bulk raised-bed soils differing ages (2, 8, 15 and 26 years) and soil surface properties was quantified to determine soil properties control OC stabilization in the raised-bed soils. The OC contents were also measured for different soil particle size fractions: clay+silt (0–50 μm), fine sand (50–200 μm), and coarse sand (200–2000 μm). Results of the study showed that the OC contents of bulk soils decreased significantly when the age of raised-bed reached to 26 years. This decrease may attribute to the changes in soil surface properties (clay content, exchangeable Ca, dithionite-extractable Fe, oxalate-extractable Fe and Al, and soil reactivity) with increasing the age of raised-beds. Reduction is OC contents was observed all soil fractions with increasing the age of raised-bed soils. The OC losses after 26 years of cultivation were 83%, 71%, and 11% in the coarse sand, fine sand and the clay+silt fractions, respectively. Results obtained in this study suggest the important role of clay+silt fraction in the long-term accumulation of OC in the raised-bed soils.