Returning crop straw to farmland is widely used to recycle nutrients and improve soil quality. But new research shows that the way straw is returned to soil can strongly influence how effectively it limits emissions of nitrous oxide, a potent greenhouse gas.
Researchers compared several straw management strategies in nitrogen-fertilized saline-alkali soil and found that pelletized straw produced the strongest reduction in nitrous oxide, or N₂O, emissions. Under low nitrogen conditions, pelletized straw reduced cumulative emissions by 45.7% compared with soil receiving no straw , while the reduction remained 43.2% under high nitrogen input .
“Our results suggest that straw return should not be treated as a single management practice,” said corresponding author Yuping Zhuge of Shandong Agricultural University. “The physical form and processing pathway of straw can alter microbial nitrogen cycling, which in turn affects how much nitrous oxide is released from soil.”
The study focused on saline-alkali soils, which are often characterized by high pH, elevated salt levels and relatively low soil organic carbon. Farmers commonly rely on nitrogen fertilizer to sustain crop production in these soils, but added nitrogen can also stimulate microbial processes that generate N₂O.
The researchers conducted a 90-day incubation experiment using soil collected from a saline-alkali land improvement demonstration site in Weifang, Shandong Province, China. Two nitrogen application rates, equivalent to 120 and 240 kilograms per hectare, were tested. The team compared soil receiving no straw with four straw-derived treatments: crushed straw, pelletized straw, composted cattle manure derived from straw-fed livestock, and carbonized straw biochar.
Higher nitrogen input increased cumulative N₂O emissions by an average of 41.6% . However, all four straw treatments reduced emissions relative to the no-straw control. Pelletized straw consistently produced the lowest cumulative emissions, whereas carbonized straw was generally less effective. The timing of emissions also changed. In soil without straw, N₂O emissions peaked around day 30, while straw-amended soils showed a delayed peak around day 60.
The researchers then examined the microorganisms involved in nitrogen cycling. They found that N₂O emissions were closely associated with the abundance of the amoA gene in ammonia-oxidizing bacteria, or AOB . Among the functional genes studied, AOB amoA showed the strongest relationship with cumulative N₂O emissions. Straw application generally reduced its abundance.
Straw addition also changed the composition of the ammonia-oxidizing bacterial community. The relative abundance of Nitrosovibrio increased, while Nitrosospira declined , indicating that straw management affected not only the number of ammonia oxidizers but also which groups dominated the community.
The findings highlight an important distinction for agricultural greenhouse gas management: returning crop residues can help reduce N₂O emissions, but the size of that benefit depends strongly on how the straw is processed and applied.
The authors conclude that pelletized straw may be particularly effective for suppressing AOB-associated N₂O production in nitrogen-fertilized saline-alkali soils. Field studies will be important for determining how these effects translate from controlled incubation conditions to working agricultural systems.
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Journal Reference: Li Z, Dong H, Liu W, Yu Y, Hernández M, et al. 2026. Straw return methods differentially mitigate N 2 O emissions with reduced AOB amoA abundance and shifted community composition in N-fertilized saline-alkali soils. Nitrogen Cycling 2: e027 doi: 10.48130/nc-0026-0014
https://www.maxapress.com/article/doi/10.48130/nc-0026-0014
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Nitrogen Cycling
Experimental study
Straw return methods differentially mitigate N2O emissions with reduced AOB amoA abundance and shifted community composition in N-fertilized saline-alkali soils
24-Sep-2026