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This study aimed to investigate the effects of a biological nitrification inhibitor on nitrous oxide emission and rice yield quality in paddy soils and its effects on denitrifying the bacteria of nosZ, nirK, and nirS types. Two treatments were performed: (1) using a local conventional fertilizer as the control CK; (2) using the partial application of a conventional fertilizer + biological nitrification inhibitor as SW. N2O emission was measured using gas chromatography; qPCR amplification was performed using primers for the targeted functional genes, nosZ, nirS, and nirK, and denitrifying functional gene abundance and denitrifying microbial community structure were analyzed using fluorescence quantification and high–throughput sequencing, respectively. The results reveal that the biological nitrification inhibitor resulted in a 41.83% reduction in N2O, relative to the normal fertilizer treatment. Meanwhile, rice yield increased by 15.45% and related quality indexes were also improved. This can promote the reproduction of bacteria with the nosZ gene while inhibiting the growth of bacteria with nirS and nirK genes. The core bacteria, Nitrosospira, Rhodanobacter, Bradyrhizobium, Tardiphaga, Rhodopseudomonas, and Paracoccus, positively correlated with N2O emissions, while core bacteria Azospirillum, Burkholderia, and Mesorhizobium negatively correlated with N2O emissions. Therefore, the application of a biological nitrification inhibitor could be an effective measure to promote rice yield and quality, reduce N2O emissions, and affect key denitrifying bacteria.

Harnessing an ammonia-oxidizing microbiome has become an increasingly attractive form of management for mitigating greenhouse gas emissions in rice paddies; however, the relationship between greenhouse gas emissions and ammonia-oxidizing microbiomes, using a nitrogen application and irrigation regime, has not been well investigated. To decipher which of (and how) the specific mmonia-oxidizing bacterial species drive the greenhouse gas CH4 and N2O emissions, a field experiment with varying nitrogen application and irrigation regimes was initiated to investigate the succession of key bacterial consortia associated with GHG emissions. The results showed that water-saving irrigation (AWD) significantly increased NO3-N and NH4+-N concentrations, compared with conventional irrigation (FDF), whereas (total nitrogen) TN was little higher in FDF (1.38 g kg−1) compared with the AWD (1.36 g kg−1). During the rice-growing season, CH4 emissions ascended speedily, and emissions peaked at maximum values of 3.32 and 4.41 ug mg−2 h−1 on day 5 in FDF and AWD irrigation regimes, respectively, and then they rapidly decreased during the midseason period, maintaining a relatively low emission rate until the rice was harvested. The patterns of N2O emission fluxes had the same tendencies with N fertilization. Putative key taxa, such as Flavobacterium, Massilia, Arenimonas, Novosphingobium, Pseudomonas, exhibited significant positive relationships with higher GHG emissions, suggesting that they make particularly obvious contributions to N2O emissions. These putative taxa should be considered when designing a high nitrogen application and irrigation strategy. As such, the nitrogen application of N180, and the irrigation regimes of water-saving irrigation, are recommended methods for N conservation and the mitigation of greenhouse gas emissions in rice paddies.

Characterizing the rhizosphere microbial community composition associated with enhanced crop yield and (or) greenhouse gases is an important first step towards understanding the role of the microbiota in rice paddies. This research aimed to decipher the influence of straw tea composting product combined with dicyandiamide amendment on greenhouse gas emission and microbial community in rice paddies.The results indicated that amendment of biological nitrification inhibitors can mitigate gas emissions and significantly increase rice yield by 41.70%, and improve the growth and development of the root system. Furthermore, composting product can mitigate greenhouse gas emissions, and bionitrification inhibitor combined with straw compost tea can effectively increase the growth and development of rice, the number of panicles, which are respectively 9.75% and 18.34%. However, the biological nitrification inhibitor impacted the communities of nitrogen-fixing bacteria (Proteobacteria), bacteria capable of eliminating nitrogen (Nitrospirae) as well as Verrucomicrobia known to be one of the most common and diverse phyla in soil habitats. As with bacteria, a distinct community structure and distribution patterns for archaea were observed in soils; however, the abundance, richness, regularity and diversity of archaea communities were significantly less in the different samples. In addition, biological nitrification inhibitors have had an impact in Euryarchaeota, responsible for the elimination of methane.

Although composting, a measure to dispose agricultural waste, is widely accepted and applied, specific knowledge of microbially driven effects on nitrous oxide (N2O) emissions during composting remains limited. Here, we monitored the impact of sawdust on N2O emissions during pig manure composting. The results suggested that adding sawdust to the compost improved the compost temperature and reduced N2O emissions. The addition of sawdust significantly altered the bacterial community structure and enhanced community turnover during the composting process. The addition of sawdust significantly reduced the relative abundance of denitrification and ureolysis, while increasing the relative abundance of nitrogen fixation. Specifically, adding sawdust may reduce N2O emissions by reducing the relative abundance of Salinithrix, Truepera, Azomonas, Iamia, Silanimonas, Phycisphaera, and Gp21 during the thermophilic and mature phases of the composting period.

Free amino acids and short peptides (FAPS) that play an important role in plant nutrition can be extracted from rapeseed meal (RSM) by microbial enzymolysis. The enzymolytic activity of one bacterial strain isolated from RSM for the production of FAPS fertilizer (FAPSF) via solid-state fermentation, as well as its detoxification activity for isothiocyanates and oxazolidinethione, was investigated in this study. The strain NJNPD41 isolated from RSM piled-soil possessed effective proteolytic activity and was identified as Bacillus flexus on the basis of its morphological, physiological, and biochemical properties, as well as 16S rDNA analysis. Compared to the uninoculated control, inoculation with the strain NJNPD41 significantly increased the yield of total free amino acids and short peptides by 115% and decreased the content of isothiocyanates and oxazolidinethione by 53% and 60%, respectively, after solid-state fermentation. The pot and field experiments showed that FAPSF significantly promoted eggplant growth and enhanced the fruit yield and quality of eggplant compared to the control. In conclusion, this study provided a novel method for the high-value utilization of RSM to produce high-quality and low-toxicity FAPSF using the newly isolated strain B. flexus NJNPD41.

The aim of this work was to study the influence of inoculation with microbial inoculants (MI) or mature compost (MC) by comparing the resultant composting efficiency with that in a noninoculated (CK) treatment. MI and MC application both accelerated the composting process according to fluorescence excitation-emission matrix (EEM) detection and germination index testing. Bacterial and fungal community composition both differed significantly over the composting period. However, the turnover of the initial bacterial community played a significant role in the composting process, and the key operational taxonomic units (OTUs) of MI (OTU_26, Thermicanus) and MC (OTU_48, Tepidimicrobium) showed significant explanatory power for the formation of humic acid-like and fulvic acid-like substances, respectively, during the stage of composting. Thus, our results indicate that microbial inoculation accelerates the composting process by stimulating key resident microbes in the initial stage.

The carbon to nitrogen ratio (C/N) is well known for its importance in the composting process, however the fiber degradation and humification associated with enzymatic activity and microbial variation derived from different C/N ratios are poorly studied. Here, we designed two treatments of chicken manure with 15% (initial C/N ratio 9.61) and 50% (initial C/N ratio 17.3) rice husk to adjust the moisture of mixtures for turning feasibly by towable fertilizer turner in industrial level. Compared to the C/N ratio 9.61, the suitable C/N ratio of 17.3 significantly enhanced the composting efficiency and the final germination index (23.7%). Moreover, the suitable C/N ratio increased the relative abundance of Bacilli, which played an important role during the mesophilic and thermophilic phases. Bacilli abundance was related to cellulose and β-glycosidase activities, thus improved fiber degradation and humification. This study not only seeks a swift method in industrial level to process chicken manure but also provides insight into the enzymatic activity of microbial community related to high-efficient composting.