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Developing best management practices for late nitrogen applications in corn

Principal Investigator: Joshua Nasielski

Research Institution: University of Guelph

Timeline: May 2021 – October 2024  


  • Identifying optimal N source, N placement and N rates for late N management.
  • Quantifying N volatilization at the Harrow Research and Development Centre using the wind tunnel method.
  • Quantifying effect of drought on efficacy of late N applications.
  • Quantifying effect of leaf burn from urea applications above the canopy.
  • Conduct an economic analysis of late N applications.
  • Develop an interactive field presentation on making in-season N management decisions.
  • Remotely sensed vegetation indices to test whether delayed N strategies cause crop effects that can be detected by well-known remote sensing indices.


  • A move towards late N application will increase the economic and environmental performance of N fertilizer use in cereal crops like corn.
  • The identification of 4R best management practices (N placement, source and rate) for late N applications and associated economic costs/benefits may increase the viability of late N management strategies.
  • Assist with better on-farm decision making, regarding the adoption of late N strategies, by quantifying the risks associated with short-term drought immediately after late N application and to identify the optimal N source/placement options to mitigate that risk.
  • Develop better late N management strategies to help reduce the negative environmental effects of N fertilizer use in agriculture and provide for improved economics of N use.
  • The quantification of costs, benefits and risks of late N applications will provide direction to help develop better government/non-government incentive programs.

Scientific Summary:

In Ontario, there is sustained farmer interest in ‘late’ or ‘delayed’ nitrogen (N) management strategies, where the bulk of fertilizer N is applied in the weeks prior to silking. Farmer interest in late N management is driven by both economic and environmental considerations: a) improved N recovery efficiency due to greater synchrony between crop N demand and soil N supply, b) reduced labour requirements during the busy planting season, and c) improved ability to account for in-season weather/soil/crop conditions and adjust N application rates. As such, late N applications can be more profitable and result in less N losses than typical practices. While proof-of-concept studies have been carried out in Ontario, agronomists and farmers have questions about the most effective 4R management decisions for late N applications to minimize losses and maximize N recovery. There is also concern about the risk of dry weather stranding N outside of the root zone, rendering late N applications ineffective, though this risk has never been quantified. Further, there is a risk of late-season surface applied N via streaming, broadcast or Y-drop being subject to ammonia volatilization losses.

This project proposes to develop best management practices for, and quantify the risks of, fertilizer N management strategies based on late N applications. It builds upon previous research done in Ontario and scales out testing, as well as interactive demonstrations, across four research stations. The project will determine 4R best management practices for late N applications using different N source, rate and placement treatments in terms of their effect on yield, N recovery efficiency and N volatilization. On a subset of treatments, rainfall exclusion shelters placed between the rows immediately after late N application will quantify the effect of a short-term drought on late N application efficacy across different N source/placement combinations. Data generated from the study will allow for an economic analysis of the risk, costs and benefits of late N applications in Ontario.

The AgriRisk Initiatives (ARI) is a five-year program delivered under the Canadian Agricultural Partnership (the Partnership).

External Funding Partners:

Agriculture and Agri-Food Canada

National Science and Engineering Research Council

Ontario Ministry of Agriculture, Food and Rural Affairs

University of Guelph