Returning Rice Straw Helps Paddy Soils Lock Away More Carbon Through Iron-Mediated Protection

Returning crop straw to farmland is widely used to recycle nutrients and improve soil quality. New research now reveals another important benefit: straw return may help paddy soils retain more organic carbon by activating two complementary forms of protection, one physical and one chemical.

Researchers from the Chinese Academy of Agricultural Sciences investigated how long-term straw incorporation affects soil organic carbon in a double-cropping rice system. Their findings show that iron oxides play a central role in connecting straw management with carbon storage.

"Our results suggest that straw return does more than simply add organic matter to soil. It also changes the way iron minerals interact with soil particles and organic carbon, creating conditions that can support longer-term carbon stabilization," said corresponding author Yinghua Duan of the Chinese Academy of Agricultural Sciences.

The study was based on a long-term field experiment established in 2012 at the Qiyang Red Soil Experimental Station in Hunan Province, China. After 11 years, the researchers compared four management treatments involving mineral fertilizer, straw return, winter green manure using Chinese milk vetch, and combinations of these practices.