Abstract:
Objective The redox state of birnessite in paddy soil can change with the soil wet-dry alternation, which affects the soil nitrogen cycle and then affects the emission of greenhouse gas nitrous oxide (N2O). The soil moisture conditions and the effect of birnessite (0.1%, w/w) on soil N2O emissions were taken as the breakthrough point to explore the mechanism of birnessite affecting soil N2O emissions under the alternation of wet and dry conditions.
Method In this study, the yellow-brown paddy soil was used as the object, and the microcosm culture experiment was carried out by applying birnessite (0.1% w/w) and using different water conditions to explore its effect on N2O emissions.
Result Within 14 days of culture, birnessite deeply promoted the cumulative N2O emissions under constant water conditions (60% and 100% field maximum water holding capacity treatments), with an increase of 11.3% and 25.3%. However, the effect of birnessite on the cumulative N2O emissions under the alternating of wet and dry conditions (100%-60% soil maximum water holding capacity) was not significant. Birnessite significantly increased the nitrite reductase (nirK)/nitrous oxide reductase (nosZ) gene copy ratio under constant water conditions. However, birnessite significantly decreased the ratio of nirK/nosZ under alternating wet and dry moisture conditions.
Conclusion The alternation of wet and dry conditions (100%-60% soil maximum water holding capacity) without birnessite or birnessite under constant water conditions can promote the release of N2O emissions from the yellow-brown paddy soil, but the alternation of wet and dry conditions (60% and 100% field maximum water holding capacity treatments) can reduce promoting effect of birnessite on N2O emissions. The effect of water conditions on N2O emissions from yellow-brown paddy soil is greater than birnessite.
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