Summary
This field study compared denitrifier microbial communities in fertigated soils under continuous soybean monocropping versus three maize-soybean rotation systems in semi-arid Northeast China. Whilst soybean rotations reduced overall denitrifier abundance compared to monocropping, they significantly increased the nirS/nirK gene ratio, suggesting potential mitigation of nitrous oxide emissions. The findings indicate that nirS-type denitrifiers are the dominant contributors to denitrification under these rotation systems, with soil organic matter driving community composition changes.
Regional applicability
The semi-arid climate and fertigated production system of Northeast China differ substantially from most United Kingdom arable conditions, which are typically temperate and predominantly rain-fed. However, the mechanistic insights regarding crop rotation effects on denitrifier community structure and the relative dominance of nirS-type bacteria may be transferable to UK cereal-legume rotations, particularly if irrigated systems expand under climate change. Further UK field validation would be needed to confirm whether similar community shifts and emission reductions occur.
Key measures
Absolute abundance of nirS- and nirK-type denitrifiers (qPCR); nirS/nirK gene ratio; community composition (high-throughput sequencing); soil nitrate reductase (NR) activity; soil nitrite reductase (NiR) activity; soil denitrification potential (SDP); soil organic matter (SOM)
Outcomes reported
The study measured the abundance and community structure of nirS- and nirK-type denitrifiers, soil enzyme activities (nitrate and nitrite reductase), and denitrification potential across four fertigated cropping systems. It assessed how crop rotation systems modified these microbial communities and their relationship to greenhouse gas production potential.
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