Modifying fertilizer rate and application method reduces environmental nitrogen losses and increases corn yield in Ontario Kamaljit Banger a , Claudia Wagner-Riddle a, ⁎, Brian B. Grant b , Ward N. Smith b , Craig Drury c , Jingyi Yang c a School of Environmental Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada b Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario K1A 0C6, Canada c Harrow Research and Development Centre, Agriculture and Agri-Food Canada, Harrow, Ontario N0R 1G0, Canada HIGHLIGHTS • Provincial N 2 O reduction was assessed for combined 4R fertilizer practices in corn. • DNDC model was used to simulate ni- trogen losses for 11 scenarios over 30- years. • Injection or side-dress increased N 2 O emission due to trade-offs with other N loss. • Nitrification + urease inhibitors re- duced N 2 O emissions by 11–16%. • Best approach is to combine N rate ad- justment with other 4R practices. GRAPHICAL ABSTRACT abstract article info Article history: Received 2 December 2019 Received in revised form 7 March 2020 Accepted 9 March 2020 Available online 10 March 2020 Editor: Paulo Pereira Keywords: Nitrogen Nitrous oxide emission Corn Fertilizer management Temperate climate Nitrogen (N) use in corn production is an important driver of nitrous oxide (N 2 O) emissions and 4R (Right source, Right rate, Right time and Right place) fertilizer practices have been proposed to mitigate emissions. However, combined 4R practices have not been assessed for their potential to reduce N 2 O emissions at the provincial- scale while also considering trade-offs with other N losses such as leaching or ammonia (NH 3 ) volatilization. The objectives of this study were to develop, validate, and apply a Denitrification-Decomposition model frame- work at 270 distinct soil-climate regions in Ontario to simulate corn yield and N 2 O emissions across eleven fer- tilizer management scenarios during 1986–2015. The results show that broadcasting fertilizer at the surface without incorporation had the highest environmental N loss which was primarily caused by NH 3 volatilization. When injected at planting or at sidedress, the NH 3 loss was reduced considerably. However, because more N was left in the soil, injection and sidedressing induced more losses by nitrate leaching and N 2 O emissions. Reduc- tion of N rate as proposed by the DNDC model did not affect crop yield but decreased leaching and N 2 O emissions. Addition of inhibitors promoted a further reduction in N 2 O emission (11–16%) although lesser than the reduction in N rate. Overall, our results emphasize that N rate adjustment following improvements in placement, use of in- hibitors, and application timings can mitigate N 2 O emissions by 42–57% and result in 3–4% greater yields com- pared to baseline scenario in Ontario corn production. © 2020 Elsevier B.V. All rights reserved. Science of the Total Environment 722 (2020) 137851 ⁎ Corresponding author. E-mail address: cwagnerr@uoguelph.ca (C. Wagner-Riddle). https://doi.org/10.1016/j.scitotenv.2020.137851 0048-9697/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv