N2O consumption, uptake, and microbial reduction processes in flooded sandy loamy paddy soils

Abstract

Sandy loamy soils are widely distributed in fluvial floodplains and experience flooding events frequently, resulting in a large amount of nitrous oxide (N₂O) emissions. This case is more serious when the soil use is changed to paddies. It is of great significance to figure out the N₂O consumption and its influencing factors in sandy loamy paddy soils to mitigate N₂O emissions. In this study, three sandy loamy paddy soils (0–5 cm) originated from lake deposits were selected (S1, S2, and S3) as objectives. A certain concentration of exogenous N₂O was added at the bottom of the flooded soil column to monitor the dynamics of N₂O and nitrogen (N₂) on the soil surface. Total N₂O consumption, N₂O uptake, and N₂ production were quantified, and the abundance of nitrous oxide reductase genes (nosZI, and nosZII) and other soil properties (ammonium-nitrogen, nitrate-nitrogen, and dissolved organic carbon [DOC] content) were analyzed. The results showed that the sandy loamy paddy soil column with a depth of 0–5 cm could intercept more than 95% of the exogenous N₂O under the flooded anaerobic condition, indicating that the three sandy loamy paddy soils all had extremely strong N₂O consumption capacities. And the increment of N₂ accounted for 68.73%–76.09% of the total N₂O consumption, which had a stronger relationship with the increase of nosZI gene abundance than nosZII gene. In addition, the total N₂O consumption and N₂ increment of S1 and S3 soils were significantly higher than those of S2 soil. This difference was mainly related to soil organic matter content, total nitrogen content, DOC consumption, and the increase of nosZI gene abundance (p < 0.05). The strong N₂O consumption potential of sandy loamy soils can provide feasible solutions for regulating N₂O emissions in a wide range of similar environments in fluvial floodplains.