Diversity and composition of methanotrophs in paddy soil as affected by different long-term fertilizer management from double-cropping paddy fields in Southern China

Methane (CH4) is the most important greenhouse gas, which was produced from paddy fields. The CH4 production and emission were affected by methane–oxidizing bacteria (methanotrophs). Therefore, it is significant to investigate the effects of fertilizer applications on the change of soil methanotrophs, which affected CH4 emission. The objective of this paper was to describe changes of CH4 and diversity and composition of methanotrophs in paddy soil in relation to the application of crop residues, mineral fertilizer, and manure based on a long-term field experiment. In this study, static chamber-gas chromatography technique, real-time polymerase chain reaction (PCR) and Illumina high-throughput sequencing of the 16S rRNA gene, respectively, were used to analyze the CH4 emissions from paddy fields, soil methanotrophs abundance and community diversity from May to October 2014 under five fertilization treatments: mineral fertilizer (MF), rice residue and mineral fertilizer (RF), low manure rate and mineral fertilizer (LOM), and high manure rate and mineral fertilizer (HOM), as compared to without fertilizer input (CK). The results indicated that CH4 from fertilization treatments displayed different emission patterns during early and late rice growth period. HOM treatment had the highest CH4 emissions during early and late rice growth period with 5.074 and 6.099 g m-2, respectively. Some methanotrophs genera (Methylosinus, Crenothrix, Methylocaldum, Methylomicrobium and Methylomonas) were identified at the early and late rice main growth stages. The abundance and composition of soil methanotrophs were affected by long-term fertilization managements. The methanotrophs abundance was inhibited under MF treatment, while they were stimulated under RF, LOM and HOM treatments. The abundance and community composition of methanotrophs in paddy soil were affected by fertilizers of mineral, crop residues, and manure. It was concluded that application with organic and crop residues enhance the abundance and community composition of methanotrophs in double-cropping paddy fields in Southern China through a long-term fertilizer experiment.