Occurrence of fermentative and respiratory dissimilatory nitrate reduction to ammonium (DNRA) in flooded rice soil ecosystems: Potential pathways for nitrogen fertilizer management through organic supplementation

Dissimilatory nitrate reduction to ammonium (DNRA) is recognized as a nitrogen retention pathway in agricultural soils. This study revealed a predominant presence of genes associated with fermentative DNRA in flooded rice soil, as indicated by functional prediction and metagenomic sequencing. Supplementing organic fertilizer to adjust carbon-to-nitrate (C/N) ratio led to distinctive microbial groups within the soil microbiomes, particularly at the highest C/N ratio (20/1) applied. Several microbial taxa were identified as possessing genes for both fermentative/respiratory DNRA and denitrification, suggesting that these soil microorganisms have the potential to maneuver nitrate reduction through various pathways that are favored under different environments.