Nitrogen Losses: A Meta-analysis of 4R Nutrient Management in U.S. Corn-Based Systems

Nitrogen Losses: A Meta-analysis of 4R Nutrient Management in U.S. Corn-Based Systems

Crops: Corn for grain
4R Practices: Metadata Project

Nitrogen Losses: A Meta‐analysis of 4R Nutrient Management in U.S. Corn‐Based Systems

Lead Researcher:

Dr. Alison Eagle


Environmental Defense Fund

Start Date: 2014

End Date: 2014

Collaborating scientists and universities

  • Dr. Lydia Olander, Duke University
  • Dr. Katie Locklier, Duke University
  • Dr. James Heffernan, Duke University
  • Dr. Emily Bernhardt, Duke University

Project Summary

Modern fertilization practices have fed the world, but unfortunately, they also contribute to serious environmental consequences – coastal dead zones and fish kills, acid rain, climate change, and stratospheric ozone destruction. These result most notably from nitrate (NO3) leaching and runoff, and nitrous oxide (N20) emissions coming from nitrogen (N) not taken up by crops. Improved fertilizer management is vital to efforts that seek to increase cropping efficiency and minimize these nutrient losses. Such improvements can enhance both farm profitability and environmental sustainability. Many studies have evaluated responses of yield to varying fertilization rates, some have measured losses of NO3 and a few have included N20 , but rarely have they considered these all together, and not in a way that accounts for multiple aspects of proper nutrient management or how these relationships vary with soil, climate, or crop type. A meta‐analysis of existing research would allow evaluation of many of these relationships and significantly enhance our understanding of what is controlling N use efficiency (NUE) and N loss pathways.

Answering these questions in a comprehensive and integrating manner will provide novel, region‐specific information that can be used to 1) estimate the magnitude of reduced fertilizer needs and reduced excess N under different scenarios of 4R management, 2) estimate the magnitude of NO3 and N2O losses under different scenarios of 4R management, 3) invest limited research dollars more strategically and 4) implement N management in ways that maintain or improve yields while minimizing environmental costs. 

Project Goals:

  • How do crop yield, NO3 leaching, and N20 emissions respond to N fertilizer application rate, timing, type, and placement? 
  • How do these effects of fertilization practices depend on climate and soil factors?

Project Results:

  • Field research on N2O and NO3 losses in corn-based systems in North America points to potential system improvements and reduced losses with a selection of 4R nutrient management practices.
  • If the standard practices tested in the field data from this meta-analysis appropriately represent those in production agriculture, nitrification inhibitors could reduce average N2O emissions by 36%, and side-dressing fertilizer instead of applying at or before planting could reduce emissions by 50%. In addition, where aqueous ammonia fertilizer is in use, average NO3 leaching reductions of 18 kg N/ha may be achieved by using UAN or urea fertilizer instead.
  • Cross-site comparisons are needed to capture both N2O and NO3 loss potential and how they relate to each other in varying regions and with different management.

Annual Reports