Reactive Nitrogen in the Biosphere

Nitrogen budgets for crop production and resulting nitrogen species released to the environment. This Article focuses on the evaluation of the four input budget terms (blue arrows) and the crop products term (green arrow), and does not assess the distribution of losses among the different reactive nitrogen forms indicated by the red arrows, or the changes in soil nitrogen stock. The sizes of the blue and green arrows are determined by estimated nitrogen budgets for the global crop production system for the period 2011-2015 (the number in parentheses is the median value of all available estimates for each nitrogen budget term from the 13 datasets). The crop products budget term includes all parts of the crop that are removed from the cropland and used for various production purposes (for example, crop grains, crop residues removed for feed). However, considering the large uncertainty related to the quantity of crop residue removed and whether this is used for productive purposes after removal, some datasets focus the assessment on crop grains only. BNF, biological nitrogen fixation; DON, dissolved organic nitrogen; PON, particulate organic nitrogen. This figure was created in PowerPoint (Microsoft).

The figure above is from Zhang et al., 2021, Nature Food (see below).

The Research Coordination Network (RCN) on reactive nitrogen (Nr) sponsored seven workshops on topics including climate-nitrogen interactions, the human health impacts of excess nitrogen in air and water, nitrogen use efficiency, air quality and ecosystem services, the management of nitrogen to produce more food with less pollution, watershed management spanning an international boundary, and harmonizing global nitrogen datasets used in Earth system models and global analyses of agriculture.

Although this RCN ended several years ago, two papers came out in 2021 that originated from workshops organized by this RCN:

Zhang et al. synthesized results from nearly thirty researchers from ten different research groups across the world, including universities, private sector fertilizer associations, and the United Nations Food and Agriculture Organization (FAO). Leaders of these groups attended a workshop organized by this RCN in New Orleans in 2017. Each research group estimated how much N is added to croplands as fertilizer and manure, how much of the added N is harvested in crops, and how much is left over as potential environmental pollution. Some surprising and troubling differences were revealed among the ten research groups, suggesting that our ability to measure, and thus manage this essential nutrient and potent pollutant is not as good as it needs to be. Digging into the data more deeply, however, many of these differences were explained by varying definitions and methods used by the different groups. This intercomparison project enables researchers, agronomists, and policy makers to identify where we can improve nitrogen budget estimates (Zhang, X. et al. (26 coauthors). 2021. Quantification of global and national nitrogen budgets for crop production. Nature Food, 2:529-540,

A press release on this publication can be found here:

The paper can also be found on the Nature web site.

Lin et al. (2021) have published a comparison of the nitrogen budgets on either side of the US-Canadian border (Washington State and British Columbia) of the Nooksack River watershed. This international, multidisciplinary, multiagency collaboration was initiated at a workshop organized by this RCN held at Western Washington University in 2016:

Lin, J., Compton, J. E., Clark, C., Bittman, S., Schwede, D., Homann, P. S., et al. (2020). Key components and contrasts in the nitrogen budget across a U.S.‐Canadian transboundary watershed. Journal of Geophysical Research: Biogeosciences, 125, e2019JG005577.

During its lifetime, this RCN facilitated a community of researchers from a wide range of disciplines to exchange information and knowledge about Nr in the environment. The RCN fostered the creative science and synthesis needed to search for well-informed and integrative mitigation strategies, and promote the communication of this science and synthesis to a broad audience of scientists and nonscientists.

This RCN project contributed to advancing the search for sustainable solutions to the challenges of managing nitrogen wisely for producing abundant and nutritious food while minimizing unintended consequences of environmental pollution and human disease. By contributing to the US National Climate Assessment (2011 workshop product), partnering with the agronomic community and fertilizer industry to create a consensus statement (2013 workshop product), linking ecosystem critical loads with economic and non-economic values of ecosystem services (2015 workshop products), publishing an overview for environmental studies students (2016 World Cafe product), coordinating in intercomparsion of global agricultural N budgets (2017 workshop and 2021 paper cited above), and organizing a trans-boundary regional effort of multiple stakeholders (2016 workshop outcome, including 2021 paper cited above), we have assembled the kinds of partnerships among diverse disciplines and stakeholder groups needed to address this wicked problem with rigorous scientific investigation and cross-disciplinary communication and collaboration.

For further reading, check out these reports & articles: