From Physical Architecture to Ecosystem Function: Tillage Exerts Indirect Control on Nitrogen Transformation by...

Area of Science:

• Soil Science
• Environmental Microbiology
• Biogeochemistry

Background:

• Tillage practices significantly impact soil structure and function.
• The degradation of preferential flow paths by tillage affects nitrogen (N) cycling.
• Understanding these changes is crucial for sustainable agriculture.

Purpose of the Study:

• To investigate how long-term tillage affects nitrogen cycling through the degradation of vadose zone preferential flow paths.
• To link soil hydraulic property changes to nitrogen functional succession.
• To provide insights for targeted nitrogen management in farmlands.

Main Methods:

• Integrated dye tracing, 15N isotope tracing, and metagenomic techniques.
• Investigation of croplands across multiple tillage chronosequences.
• Path analysis to determine relationships between hydraulic properties, community shifts, and N processes.

Main Results:

• Tillage homogenizes the vadose zone and reshapes nitrogen-cycling communities, favoring nirS- over nirK-denitrifiers.
• Nitrification rates are higher in preferential paths (short-term tillage), while denitrification and DNRA dominate in the matrix (long-term tillage).
• Anammox was observed only in the matrix under medium- and long-term tillage.

Conclusions:

• Tillage-driven soil degradation redirects nitrogen pathways from nitrification to reductive N loss.
• This shift converts systems prone to nitrate leaching into those with higher gaseous emission potential.
• A mechanistic link between soil hydraulic degradation and nitrogen functional succession was established, supporting stage-dependent nitrogen management.