Nitrogen and carbon addition changed nitrous oxide emissions from soil aggregates in straw-incorporated soil

Purpose The effects of straw incorporation on soil nitrous oxide (N2O) emission at the soil aggregate scale have yet to be elucidated, especially with supplemental nitrogen (N) and/or organic carbon (OC). The objective of this study was to evaluate N2O emission across different size soil aggregates of 6-year straw-incorporated soil as affected by exogenous N and OC treatments. Materials and methods In the present study, the N2O emission from different particle size soil aggregates (> 2, 1-2, 0.25-1, and < 0.25 mm) were investigated with/without 6-year maize straw incorporation under protected vegetable production. Ammonium sulfate (100 mg N kg(-1)) or ammonium sulfate (100 mg N kg(-1)) + glucose (100 mg C kg(-1)) were applied to these soil aggregates along with an unamended treatment (Control, CK) and incubated in a robotized continuous on-line incubation system for 200 h at 20celcius and 25% gravimetric water content. The dynamics of N2O emission was conducted in closed bottles with 21% initial oxygen concentration. Results and discussion The results showed that the proportion of > 1 mm aggregates and < 1 mm aggregates in straw-incorporated soil were increased 10.2% and decreased 29.1%, respectively, than those in no straw-incorporated soil. For all investigated treatments, < 0.25 mm aggregates had the highest cumulative N2O emission with 2.15-45.1 nmol N g(-1) across all aggregate sizes. Cumulative N2O emission in < 0.25 mm aggregate of straw-incorporated soil was greater than that in no straw-incorporated soil without exogenous N and OC addition. N addition stimulated N2O emission from all size aggregates, and the N-stimulating effects were enhanced by the simultaneous addition of glucose. With exogenous N, N, and OC additions, cumulative N2O emission in > 2 mm, 1-2 mm, and 0.25-1 mm aggregates of straw-incorporated soil was greater than that in no straw-incorporated soil. Conclusions These results suggested that the characteristic of N2O emissions across different size aggregates from straw-incorporated soil is altered with supplemental N and OC. The study highlights that the N2O emission from straw-incorporated soil was stimulated by exogenous organic carbon and nitrogen addition within > 0.25 mm aggregate.

Automated summary

The study shows that the emissions of N2O from straw-incorporated soil are influenced by exogenous nitrogen and organic carbon, leading to changes in N2O emissions across different size aggregates.