Reactive nitrogen losses from Canadian agricultural soils over 36 years

J.Y. Yang, C.F. Drury, R. Jiang, D.E. Worth, S. Bittman, B.B. Grant and W.N. Smith

Ecological Modelling, 2024, vol. 495, issue C

Abstract: Agriculture is a major source of reactive nitrogen (Nr) losses through ammonia (NH3) volatilization, nitrous oxide (N2O) emissions and nitrate (NO3−) leaching. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the nitrogen (N) balance in soils, including N removals by harvested crops and Nr losses for the years 1981–2016 across Canada. Annual N inputs to farmland include commercial fertilizer N, livestock manure N, symbiotic and asymbiotic biological N fixation and atmospheric N deposition of NOx and NH3. The total annual N input for Canadian farmland was 5528 Gg N (103.2 kg N ha−1) in 2016 where N removal by crops and Nr accounted for 72.5 % (74.9 kg N ha−1) and 13.4 % (13.9 kg N ha−1), respectively. The Nr losses from N2O emissions, NH3 volatilization and NO3− leaching accounted for 64 Gg N (1.2 kg N ha−1), 330 Gg N (6.2 kg N ha−1) and 348 Gg N (6.5 kg N ha−1), which represents between1.2–6.3 % of total N input. A total of 777 Gg N (14.5 kg N ha−1) remained in the soil as surplus N (14.1 % of total N input), which could be available to subsequent crops in dryer regions but might be subject to N2O loss through nitrification or denitrification processes or NO3− leaching following heavy rains in humid regions. Nitrous oxide and ammonia emissions increased over a 36-year period due to increased fertilizer N inputs. The percentage of N inputs that was estimated to be lost as Nr increased from 17.9 % in 1981 to the peak level of 19.8 % in 2001 and then declined to 13.4 % in 2016. Total N removal by crops increased at a greater rate than N input during the 2001–2016 period resulting in an increased N uptake by crops over the last 15 years. The improved management of fertilizer N for agricultural systems represents a key opportunity for both farmers and policy makers to further reduce Nr losses from Canadian farmland without negatively impacting productivity.

Keywords: Reactive nitrogen; Nitrous oxide emission; Ammonia emission; Nitrate leaching; Surplus nitrogen (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:ecomod:v:495:y:2024:i:c:s0304380024001972

DOI: 10.1016/j.ecolmodel.2024.110809

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