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.