Nitrate addition inhibited methanogenesis in paddy soils under long-term managements

Abstract

Rice fields are a major source of atmospheric methane (CH<sub>4</sub>). Nitrate has been approved to inhibit CH<sub>4</sub> production from paddy soils, while fertilization as well as water management can also affect the methanogenesis. It is unknown whether nitrate addition might result in shifts in the methanogenesis and methanogens in paddy soils influenced by different practices. Six paddy soils of different fertilizer types and groundwater tables were collected from a long-term experiment site. CH<sub>4</sub> production rate and methanogenic archaeal abundance were determined with and without nitrate addition in the microcosm incubation. The structure of methanogenic archaeal community was analysed using the PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) and pyrosequencing. The results showed that nitrate addition significantly decreased the CH<sub>4</sub> production rate and methanogenic archaeal abundance in all six paddy soils by 70–100% and 54–88%, respectively. The quantity, position and relative intensity of DGGE bands exhibited differences when nitrate was added. Nitrate suppressed the growth of methanogenic archaeal species affiliated to Methanosaetaceae, unidentified Euryarchaeota, Thaumarchaeota and Methanosarinaceae. The universal inhibition of nitrate addition on the methanogenesis and methanogens can be adopted as a practice of mitigating CH<sub>4</sub> emission in paddy soils under different fertilization and water managements.