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Managing 4R’s in corn under high surface residue conditions

Principal Investigator: Craig Drury

Research Institution: Agriculture and Agri-Food Canada

Timeline: April 2021 – July 2025  


  • To develop 4R management systems to overcome N limitations when planting corn into a standing cover crop.
  • Determine if improved placement and/or use of a new urease and nitrification inhibitor could decrease ammonia volatilization and nitrous oxide emission losses from soils.
  • To determine if cover crops, improved enhanced efficiency fertilizers and N application methods could improve nutrient uptake, yields and profitability of growing corn.
  • Develop models to simulate 4R nutrient management strategies for conservation agriculture systems with cover crops. Data will also be used for economic analysis including a partial budget to assess the impacts of the cover crop and 4R management practices that will be examined.


  • The development of a 4R practice for cover crops which enhances N uptake and yields in corn.
  • The development of an effective N placement and inhibitor combination to reduce ammonia volatilization losses by at least 75% and N2O emissions by at least 25%.
  • Determine the changes in key microbes following herbicide application to the cereal rye cover crop and following the adoption of 4R practice to corn (i.e., improved placement and the use of a longer-lasting inhibitor).
  • Determine if spring zone tillage is required to enhance corn grain emergence following the termination of the cereal rye cover crop.
  • Combine the advantages of conservation tillage with 4R practices into a profitable management system which is transferred to Ontario corn growers.

Scientific Summary:

Cover crops are the new panacea to improve soil health, enhance C sequestration and soil biodiversity, to capture residual N in the fall and to reduce nutrient runoff and leaching. However, farmers have reported problems with managing the subsequent planting of field crops such as corn into standing cover crops. One issue is the N deficiencies caused by the decomposing cover crops on the newly planted annual crop due to N immobilization during crop residue breakdown. Secondly, laboratory studies have found enhanced ammonia volatilization due to increased surface urease activities resulting from the elevated plant residue levels. We plan to build on the successes we have achieved with 4R management in conventional farming practices to enable farmers to enhance crop productivity while minimizing both ammonia volatilization losses and nitrous oxide emissions using cover crops and conservation agricultural practices.

We propose to use the newly developed double slot injection system for conventional tillage without cover crops and adapt these treatments for managing N application in a cover crop/conservation tillage field trial. We will also evaluate a newly released longer-lasting nitrification/urease inhibitor and compare this to a regular N treatment (liquid UAN or to broadcast urea or SuperU). We plan to evaluate the effectiveness of these new technologies to enhance corn yields and reduce ammonia volatilization losses using wind tunnels and nitrous oxide emissions using static chambers. The impact of the cover crop on relevant biological functions (N mineralization functions, beneficial fungal communities) pre/post herbicide and N application will also be evaluated. We planted an annual cereal cover crop in the fall of 2020 on selected plots and we will evaluate 4R management treatments in the spring/summer 2021. This study will be repeated in 2022 and 2023 field seasons to examine the impacts of variable weather patterns on N losses and crop performance.    

External Funding Partners:

Agriculture and Agri-Food Canada

Fertilizer Canada