Abstract
Rice-frog cultivation is a traditional farming system in China and has been reintroduced as an agricultural practice in China in recent years. The microbial community in paddy rhizospheric soils has attracted much attention because many microorganisms participate in functional processes in soils. In this study, Illumina MiSeq sequencing-based techniques were used to investigate soil microbial communities and functional gene patterns across samples obtained by conventional rice cultivation (CR) and rice-frog cultivation (RF). The results showed that RF significantly affected the microbial community composition and richness, which indicated that the rhizospheric microorganisms responded to the introduction of tiger frogs into the paddy fields. Operational taxonomic units (OTUs) from Sandaracinaceae, Anaerolineaceae, Candidatus Nitrososphaera, Candidatus Nitrosotalea, Candidatus Nitrosoarchaeum and some unclassified OTUs from Euryarchaeota and Agaricomycetes were significantly enriched by RF. The abiotic parameters soil organic carbon (SOC), nitrate nitrogen (NO3−-N), and available phosphorus (AP) changed under RF treatment and played essential roles in establishing the soil bacterial, archaeal, and fungal compositions. Correlations between environmental factors and microbial communities were described using network analysis. SOC was strongly correlated with Anaerolineaceae, Methanosaeta, and Scutellinia. NO3−-N showed strong positive correlations with Opitutus, Geobacter, and Methanosaeta. NH4+-N was strongly positively associated with Sideroxydans, and TN was strongly positively correlated with Candidatus Nitrotoga. Compared to conventional CR, RF greatly enriched specific microbial taxa. These taxa may be involved in the decomposition of complex organic matter and the transformation of soil nutrients, thus promoting plant growth by improving nutrient cycling. The unique patterns of microbial taxonomic and functional composition in soil profiles suggested functional redundancy in these paddy soils. RF could significantly affect the bacterial, archaeal, and fungal communities though changing SOC and AP levels.
Highlights
In most developing countries, agriculture is the main source of food, employment, income and nutrition (Saiful Islam et al, 2015)
NH4+-N was strongly positively associated with Sideroxydans and Methylosarcina from Proteobacteria, Methanobacterium from Euryarchaeota, and Cochliobolus from Ascomycota
total N (TN) was strongly positively correlated with Candidatus Nitrotoga from Proteobacteria
Summary
Agriculture is the main source of food, employment, income and nutrition (Saiful Islam et al, 2015). It is necessary to sustainably increase grain production, achieve food self-sufficiency and improve the wellbeing of small-scale farmers (Berg and Tam, 2018). This growth in food production must be achieved by reducing the use of land, water, labor and chemicals (Doss, 2010; Yuan et al, 2017). Many studies have described the ecosystems of rice-fish, rice-turtle, rice-duck, and rice-frog cultivation and have shown how these practices reduce the use of chemical fertilizers and pesticides (Li et al, 2008; Hu et al, 2016; Zhang et al, 2016; Yang et al, 2018). Rice-frog cultivation is an ancient farming system adopted by Asian farmers for many years, this innovation may have the potential to keep up with the surge in food security demand (Sha et al, 2017)
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