Impairment of groundwater quality is increasingly threatening the natural environment in part due to the incidence of eutrophication from agricultural nitrogen. Despite billions of dollars invested in improving water quality and other global conservation measures, the results have been minimal.

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These supposed failures also impact human health and can be partly attributed to nitrogen inherited from decades of cumulative agricultural intensification, which can hamper water quality improvement strategies. These delays in improving water quality must be taken into account in all future strategies.

Now a group of researchers led by a team from the University of Waterloo in Ontario have created a new method to tackle nitrogen pollution and improve water quality. Published in the journal nature geoscience, researchers sought to better understand the role of residual nitrogen in water quality levels in order to leverage better policy and improve environmental outcomes.

Six point strategy

The team defined a six-point strategy as a call to action to accelerate water quality improvements. The strategy was created as a way to recognize that these legacies and problems persist and to find ways to improve existing knowledge.

It is essential that we develop methodologies to quantify N [nitrogen] inheritances and shifts. Such estimates are essential not only for managing expectations and setting appropriate policy targets, but also for designing conservation measures that can help minimize lag times.

Nandita Basu, Professor of Earth and Environmental Sciences and Civil and Environmental Engineering, University of Waterloo

Previous nitrogen reduction management efforts have proven unsuccessful due to the length of time nitrogen can be present in the water – an effect known as nitrogen inheritance – making attempts spent seeming in vain due to poor results.

However, the six-point strategy developed by the researchers aims to tackle these problems and propose solutions that can be implemented by governments, policymakers and competent authorities.

  • Quantify latency and adjust retention expectations
  • Discover ways to use legacy nitrogen as a resource
  • Spatial and localized targeting of watershed conservation measures
  • Couple field-scale and downstream measurements to minimize latency
  • Diversify monitoring to assess results and inform adaptive management through follow-up actions
  • Better integrate assessments of short- and long-term benefits into economic analyzes

Managing Nitrogen Legacies

Managing nitrogen legacies is not a catchall approach as they depend on local factors such as climate, land management strategies and historical land use. These legacies have built up in anthropogenic landscapes over decades and pose a real threat to the diversity of ecosystems and human health.

While many conservation efforts are trying to turn back the clock on this problem, existing strategies are not diverse enough to keep up with the ongoing and increasing use of nitrogen in agriculture.

It is, therefore, vitally important to distinguish between different types of nitrogen accumulation as legacy nitrogen can build up in various environments, including ground water, soil, reservoirs, lake and stream sediments and even landfills.

Thus, building effective models that track nitrogen legacies and predict lag times will help policymakers in their efforts to improve overall water quality. 

Better spatial targeting can be achieved in a variety of ways, including better dissemination of information regarding geographically appropriate management practices and the use of strong economic incentives to strategically drive adoption of new practices in targeted locations. 

Nandita Basu, Professor of Earth and Environmental Sciences and Civil and Environmental Engineering, University of Waterloo

The six-point strategy, as previously highlighted and detailed in the study, could present promising opportunities to develop both widespread and localized tactics that mitigate the overall environmental impact of nitrogen and help improve water quality.

References and Further Reading

Basu, N. and Van Meter, K., et al., (2022) Managing nitrogen legacies to accelerate water quality improvement. Nature Geoscience, [online] 15(2), pp.97-105. Available at:

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