Changes in rhizosphere microbiomes of field-grown rice in response to biogas slurry application

Biogas slurry (BS) is widely used as a liquid fertilizer in paddy fields. A growing body of evidence shows that rhizosphere microbiota is important for plant growth and reproduction. However, the dynamic responses of rhizosphere microbiomes of field-grown rice to BS application still remain unknown. In this study, a field experiment was conducted to further understand the impacts of BS fertilizer (BCF) on the dynamic changes of rhizosphere microbiota throughout the life cycle of rice with conventional chemical fertilizer (CF) treatment as control. The results demonstrated that BS could increase the N-, P- and C- level in paddy water as well as rhizospheric microbial abundance and diversity of paddy fields compared with control. In particular, the phosphate-solubilizing- and cellulose-decomposition-related bacteria (e.g. Bacillus ) and fungi (e.g. Mortierella ) were more abundant in the rhizosphere of BCF than those of CF. Moreover, these above-mentioned microbes increased markedly at the reproductive stages compared with those at vegetative stages in BCF, which could promote rice to obtain available nutrient (phosphorus and carbon) at low fertility input stages (the reproductive stages). It was noted that denitrifying-related bacteria (e.g. Steroidobacteraceae ) decreased and dissimilatory nitrate reduction to ammonia (DNRA) -related bacteria increased generally at the reproductive stages, which could reduce N-loss and help to N-fixation. Furthermore, correlation network showed that nutrient-cycles-related microbes were more closely interconnected in BCF than control. These observations demonstrated the application of BS could regulate root-related microbiomes towards a beneficial fertilizer use for rice production.