Soil Carbon Dynamics in Paddy Ecosystems

Paddy ecosystems represent unique environments characterised by alternating waterlogged and drained soil conditions that profoundly influence the accumulation, stabilisation and turnover of soil carbon. The interplay of periodic flooding, anaerobic redox cycles and management practices such as straw incorporation and tillage modulates both the quantity and quality of soil organic carbon (SOC). Under flooded conditions, the depletion of oxygen slows microbial decomposition, promoting the formation of partially decomposed organic matter and enhancing the recalcitrant carbon pool. Conversely, drainage events stimulate oxidative processes that release greenhouse gases and mineralise labile carbon pools. Over long timescales, continuous rice cultivation drives the evolution of soil structure, favouring the formation of macroaggregates that physically protect organic matter and foster microbial hotspots. The balance between carbon inputs from crop residues and root exudates and carbon losses via respiration, leaching and methane emissions underpins the capacity of paddy fields to function as net carbon sinks. Global assessments indicate that sustainable water and residue management can enhance SOC sequestration, mitigate climate warming and improve soil fertility in major rice‐producing regions.

Research from Nature Portfolio

Recent studies have demonstrated that conversion of freshwater wetlands to paddy fields not only alters microbial community composition but also modulates carbon and nitrogen cycling. One investigation in coastal wetlands showed that the transition to rice paddy led to an initial surge in microbial biomass under aquaculture and cropping regimes but a decline under urban land use, indicating that land‐use trajectories strongly govern carbon accumulation and decomposition pathways. Variations in microbial phospholipid fatty acid profiles were linked to shifts in substrate availability and redox status, thereby affecting the rates of organic carbon mineralisation and stabilisation. Another study explored iron oxide dynamics in chronosequences of calcareous and acidic parent materials under continuous rice cultivation, revealing that redox‐driven Fe redistribution shapes soil profile differentiation. Prolonged alternating submergence and drainage fostered development of pedogenic horizons, while parent‐material characteristics determined the pace of transformation. These results underscore the coupling between redox processes, mineral reorganisation and long‐term carbon sequestration in paddy soils.

Soil Carbon Dynamics in Paddy Ecosystems publication trend

The graph below shows the total number of articles in soil carbon dynamics in paddy ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Soil organic carbon (SOC): The pool of organic carbon compounds present within soil, originating from plant residues, root exudates and microbial biomass.

Redox conditions: The oxidation–reduction status of soil, determined by oxygen availability, that drives biochemical transformations of carbon and metals.

Macroaggregates: Large soil aggregates (typically >250 µm) that physically enmesh organic matter, enhancing carbon protection and microbial habitat heterogeneity.

Labile carbon: The fraction of SOC that is readily decomposed by microbes, supplying energy and nutrients for soil biota.

Recalcitrant carbon: The portion of SOC that is chemically or physically resistant to decomposition, contributing to long‐term carbon storage.

References

1. Coastal reclamation alters soil microbial communities following different land use patterns in the Eastern coastal zone of China. Scientific Reports (2021).
2. Phases and rates of iron and magnetism changes during paddy soil development on calcareous marine sediment and acid Quaternary red-clay. Scientific Reports (2018).
3. Microbial activity promoted with organic carbon accumulation in macroaggregates of paddy soils under long-term rice cultivation. Biogeosciences (2016).
4. Spatial Variation of Soil Organic Carbon and Total Nitrogen in the Coastal Area of Mid-Eastern China. International Journal of Environmental Research and Public Health (2017).