Quantifying nitrogen loss hotspots and mitigation potential for individual fields in the US Corn Belt with a metamodeling approach

Taegon Kim, Zhenong Jin, Timothy M. Smith, Licheng Liu, Yufeng Yang, Yi Yang, Bin Peng, Kathryn Phillips, Kaiyu Guan, Luyi C. Hunter, Wang Zhou

Research output: Contribution to journalArticlepeer-review


The high productivity in the US Corn Belt is largely enabled by the consumption of millions of tons of manufactured fertilizer. Excessive application of nitrogen (N) fertilizer has been pervasive in this region, and the unrecovered N eventually escaped from croplands in forms of nitrous oxide (N2O) emission and N leaching. Mitigating these negative impacts is hindered by a lack of practical information on where to focus and how much mitigation potential to expect. At a large scale, process-based crop models are the primary tools for predicting variables required by decision making, but their applications are prohibited by expensive computational and data storage costs. To overcome these challenges, we built a series of metamodels to learn the key mechanisms regarding the carbon (C) and N cycle from a well-validated process-based biogeochemical model, ecosys. The trained metamodel captures over 98% of the variability of the ecosys simulated outputs for 99 randomly selected counties in Iowa, Illinois, and Indiana. To identify hotspots with high mitigation potential, we introduce net societal benefit (NSB) as an indicator for synthesizing the loss in yield and social benefits through emissions and pollutants avoided. Our results show that reducing N fertilizer by 10% leads to 9.8% less N2O emissions and 9.6% less N leaching at the cost of 4.9% more SOC depletion and 0.6% yield reduction over the study region. The estimated total annual NSB is $395 M (uncertainty ranges from $114 M to $1271 M), including $334 from social benefits (uncertainty ranges from $46 M to $1076 M), $100 M from saving fertilizer (uncertainty ranges from $13 M to $455 M), and -$40 M due to yield changes (uncertainty ranges from -$261 M to $69 M). For the median scenario, we noted that 20% of the study area accounts for nearly 50% of the NSB, and thus represent hotspot locations for targeted mitigation. Although the uncertainty range suggests that developing such a high-resolution framework is not yet settled and the scenario based estimations are not appropriate to inform the management practices for individual farmers, our efforts shed light on the new generation of analytical tools for life cycle assessment.

Original languageEnglish (US)
Article number075008
JournalEnvironmental Research Letters
Issue number7
StatePublished - Jul 2021


  • metamodel
  • mitigation potential
  • nitrogen loss
  • sustainable agriculture
  • the Corn Belt

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Environmental Science
  • Public Health, Environmental and Occupational Health


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