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Agricultural industry

Denitrification in the Vadose Zone: New Insights from Agricultural Managed Aquifer Recharge Study

Strategic Insights

— 1 min read

Research conducted at the University of California Santa Cruz has shed new light on the potential of the vadose zone to attenuate nitrate (NO3-) via denitrification under agricultural managed aquifer recharge (AgMAR) conditions. The study, funded by the National Institute of Food And Agriculture and the Almond Board of California, aimed to investigate biogeochemical controls on denitrification in surface soils and subsurface sediments during AgMAR. The findings suggest that the vadose zone has the potential to attenuate NO3- via denitrification, but further research is needed to determine denitrification rates in-situ.

Key Takeaways:

  • The study found that denitrification potential assays resulted in four times more N2O production near the surface, and 49 times more N2O production in the subsurface compared to the control.
  • Even without additions of carbon (C), sediments were able to denitrify 40% of the NO3- present in the subsurface during the incubation.
  • The study measured an average absolute increase of 4.0 in δ15N of NO3- across 4m depth, suggesting denitrification following AgMAR.
  • The results suggest that the vadose zone has the potential to attenuate NO3- via denitrification, but further research is needed to determine denitrification rates in-situ.
  • The study highlights the importance of quantifying denitrification rates in-situ during and immediately following AgMAR events.

Statistics:

  • 4 times more N2O production near the surface in denitrification potential assays compared to the control.
  • 49 times more N2O production in the subsurface in denitrification potential assays compared to the control.
  • 40% denitrification of NO3- present in the subsurface without C additions.
  • 4.0 average absolute increase in δ15N of NO3- across 4m depth, suggesting denitrification following AgMAR.

Sources:

  • Denitrification in the deep vadose zone: implications for nitrate leaching under agricultural managed aquifer recharge. Geoderma, 2025, 460():117457.
  • University of California Santa Cruz, Environmental Studies, Hannah Waterhouse, Corresponding author.

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