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Carbon amendment drives microbial community to favor dissimilatory nitrate reduction to ammonium over denitrification in paddy soil
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DOI：10.1016/j.ejsobi.2026.103835.png)
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Abstract
En 中文
Denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA) are microbially mediated processes that compete for nitrate in soil systems, with critical implications for nitrogen retention and environmental management. Although laboratory studies have proposed that C/N is a key regulator governing the competition between DEN and DNRA, the multi-layer microbial validation of this competition within complex soil ecosystems remains underexplored. This study used paddy fertilizer guidelines to optimize C/N, investigating the effect of carbon amendment on nitrogen retention under a fixed nitrogen fertilizer application rate. Based on baseline nitrogen fertilizer, adding 150 kg C ha−1 reduced N2O emissions by 11.3% and increased NH4+-N contents by 78.3% compared to CK. qPCR targeting nirK and nrfA genes corroborated the functional shift in microbial processes. Carbon amendment reshaped microbial networks, inhibiting core DEN drivers (e.g., Agrobacterium, Achromobacter, Aquibium) while enriching DNRA drivers (e.g., Anaeromyxobacter, Myxococcus, Geobacter), thereby favoring DNRA over DEN. To validate the functional roles of these taxa, representative DEN strains (Agrobacterium sp. D1, Achromobacter sp. D2) and DNRA strains (Myxococcus sp. N1, Anaeromyxobacter sp. N2) were obtained and introduced into pot experiments. Results demonstrated that combining DNRA strains with carbon amendment tends to facilitate paddy growth, whereas DEN strains may impair growth. In summary, this study demonstrated that carbon amendment drives the microbial community in paddy soils to favor DNRA over denitrification. It provides theoretical support for understanding the microbially driven nitrogen transformation in complex environmental soil and lays a foundation for developing novel fertilization strategies through nitrogen-carbon regulation.
Keywords:
carbon amendment
dissimilatory nitrate reduction to ammonium
denitrification
microbial community
nitrogen retention
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