Abstract
The flooding-drying cycle can cause obvious increases of nitrous oxide (N2O) emissions from paddy soil. However the relationships between N2O flux and N2O concentrations in soil and the microbial driving mechanisms during the flooding-drying process are unclear. In this study, a flooding-drying incubation experiment was carried out with a paddy soil. The topsoil (0–6cm) was divided into 6 micro-sublayers each of 1cm depth which were sampled independently. Terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative polymerase chain reaction (qPCR) were employed to determine the community composition and abundance of nitrifiers and denitrifiers, respectively. Results showed that the dynamics of N2O flux were more closely related to the N2O concentrations at 2–3cm in comparison with that at 4–5cm depth in the soil profile. During the peak period of N2O flux, the top three micro-sublayers (0–3cm) simultaneously harbored significantly higher ammonia oxidizing bacteria (AOB) population sizes, and contained higher nitrate and lower ammonia concentrations. Therefore, the top soil (0–3cm) possesses a strong ability to produce nitrate substrate for denitrification during the flooding-drying process, and the drying surface soil, with O2 penetration, favoured N2O generation. In contrast, although the bottom soil (4–6cm) contained abundant nitrate reductase gene (narG) copy numbers, it maintained low levels of AOB abundance, which could suggest that low nitrifying activity would be the major restriction limiting N2O production in this layer. In conclusion, the flooding-drying process induced significant N2O emissions from the paddy soil, which were closely related to the increasing nitrifying capability in the topsoil within 0–3cm and the dynamics of N2O concentrations at 2–3cm depth.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.