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Agriculture produces food, fiber and biofuels for the world's growing population, however, agriculture can be a major contributor of nitrogen (N) losses including emissions of ammonia (NH 3 ), nitrous oxide (N 2 O) and nitrate (NO 3 - ) leaching and runoff. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the soil N balance in 3487 soil landscape of Canada polygons from 1981 to 2016. The CANBNr model integrates NH 3 emission from fertilizers, manure from housing, storage and field, as well as direct/indirect N 2 O emissions from fertilizers, manures, crop residues and soil organic matter. The NO 3 - leaching is estimated based on the residual soil N (RSN) at harvest and drainage derived with the DeNitrification-DeComposition (DNDC) model. From 1981 to 2016, the N input from fertilizer and N fixation increased at a greater rate than N removal in harvested crops in all provinces of Canada, resulting in an increase in the RSN and N losses. In 2016, the Prairie provinces had lower N losses (11.7 kg N ha -1 ) from N 2 O, NH 3 and NO 3 - compared with 43.2 kg N ha -1 in central Canada, and 76.5 kg N ha -1 in Atlantic Canada. However, the Prairie provinces had 84.3% of the total Canadian farmland (74.3% of the total Canadian N input), while central Canada had 12.9% of Canadian farmland (21.7% of the total Canadian N input). In the Prairie provinces, the total N 2 O loss from fertilizer N ranged 4.4-8.6 Gg N whereas NH 3 loss ranged from 17.1 to 44.6 Gg N and these values were influenced by both emission intensity and total land area. Total N 2 O losses from manure were highest in Alberta, Ontario and Quebec resulting in 4.8, 4.4, and 3.4 Gg N and NH 3 losses from manure were also highest in these 3 provinces at 61.1, 45.2 and 40.4 Gg N, respectively. Nitrate leaching was impacted by drainage volumes, soil type and N inputs. In the non-growing season, NO 3 - leaching losses (36-yr average) were 63.3 Gg in Ontario and 57.5 Gg N in Quebec compared with 20.8 Gg N for Ontario and 35.5 Gg N for Quebec in the growing season. In contrast, the Prairie provinces showed higher NO 3 - leaching in the growing season (23.1-37.4 Gg N) than in the non-growing season (10.4-13.7 Gg N). In summary, total fertilizer N increased the most over the 36 years in the Prairies which resulted in increased RSN and N leaching losses that will require further intervention., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Process-based models are effective tools for assessing the sustainability of agricultural productivity and environmental health under various management practices and rotation systems. The objectives of this study were to (1) calibrate and evaluate the DeNitrification-DeComposition (DNDC) model using measurements of yields, nitrogen (N) uptake, soil inorganic N, soil temperature, soil moisture and nitrous oxide (N 2 O) emissions under long-term fertilized continuous corn (CC) and corn-oats-alfalfa-alfalfa (COAA) rotation systems in southwest Ontario from 1959 to 2015, Canada, and (2) explore the impacts of four diverse rotation systems (CC, COAA, corn-soybean-corn-soybean (CSCS) and corn-soybean-winter wheat (CSW)) on corn yields and annual N 2 O emissions under long-term climate variability. DNDC demonstrated "good" performance in simulating corn, oats and alfalfa yield (normalized root mean square error (nRMSE) < 20%, Nash-Sutcliffe efficiency (NSE) > 0.5 and index of agreement (d) > 0.8). The model provided "fair" to "good" simulations for corn N uptake and soil inorganic N (NSE > 0.2 and d > 0.8), and also daily soil temperature and soil moisture (nRMSE <30% and d > 0.7) for both calibration and validation periods. The model demonstrated "good" performance in estimating daily and cumulative N 2 O emissions from both the continuous and rotational corn, whereas it produced "poor" to "good" predictions for N 2 O emissions from the rotational oats and alfalfa crops, however, the emissions from these crops were very low and the relative magnitude of these emissions between all crops investigated were well predicted. The lowest N 2 O emissions were from COAA followed by CSCS, CSW then CC. The highest corn yields were from COAA, followed by CSW, CSCS, then CC. This study highlights how modelling approaches can help improve the understanding of the impacts of diversified rotations on crop production and greenhouse gas emissions and contribute towards developing policies aimed at improving the sustainability and resiliency of cropping systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Concerns about ammonia (NH 3 ) losses from nitrogen (N) mineral fertilizers have forced policymakers to set emission reduction commitments across Europe. Although best available techniques (BATs) have been recommended, large uncertainties still exist due to poorly targeted site-specific approaches that might compromise their effectiveness. Here we proposed and tested a conceptual framework designed to identify most effective BATs that reduce NH 3 at the site-specific level. The study was conducted in the Veneto region, northeast Italy. After the mapping of NH 3 emission potential areas, BATs and business-as-usual N fertilization scenarios were assessed using a modified version of the DNDC agroecosystem model and compared with urea broadcast distribution under different pedo-climatic conditions. The most promising practices were further tested in a field experiment using a wind tunnel combined with a FTIR gas analyzer. Results showed that closed-slot injection reduced NH 3 emissions with any type of mineral or organic fertilizers. Injected application, with ammonium nitrate or organic fertilizers, reduced NH 3 loss in maize by 75% and 96%, respectively, and in winter wheat by 87% and 98%, compared to surface broadcast. Injection was the most promising technology to support, being already available to farmers. However, some increase in nitrate leaching was observed, mostly in case of winter wheat (+24% for AN injection; +89% for organic fertilizers). By contrast, urea incorporation with hoeing, the most common technique used by farmers in spring crops, did not show satisfactory results, because the partial burial of urea caused strong NH 3 emissions that were even higher compared to surface broadcast. Recommended NH 3 reduction techniques should be tailored to local pedo-climatic and management conditions, and evaluated, in a holistic approach, considering all N fluxes in the environment., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

It is uncertain whether process-based models are currently capable of simulating the complex soil, plant, climate, manure management interactions that influence soil nitrous oxide (N 2 O) emissions from perennial cropping systems. The objectives of this study were (1) to calibrate and evaluate the DeNitrification DeComposition (DNDC) model using multi-year datasets of measured nitrous oxide (N 2 O) fluxes, soil moisture, soil inorganic nitrogen, biomass and soil temperature from managed grasslands applied with manure slurry in contrasting climates of Canada, and (2) to simulate the impact of different manure management practices on N 2 O emissions including slurry application i) rates (for both single vs. split); and ii) timing (e.g., early vs. late spring). DNDC showed "fair" to "excellent" performance in simulating biomass (4.7% ≤ normalized root mean square error (NRMSE) ≤ 29.8%; -9.5% ≤ normalized average relative error (NARE) ≤ 16.1%) and "good" performance in simulating soil temperature (13.2% ≤ NRMSE ≤ 18.1%; -0.7% ≤ NARE ≤ 10.8%) across all treatments and sites. However, the model only showed "acceptable" performances in estimating soil water and inorganic N contents which was partially attributed to the limitation of a cascade water sub-model and inaccuracies in simulating root development/uptake. Although, the DNDC model only demonstrated "fair" performance in simulating daily N 2 O fluxes, it generally captured the impact of the timing and rate of slurry application and soil texture (loam vs. sandy loam) on total N 2 O emissions. The DNDC model simulated N 2 O emissions from spring better than split manure application (fall and spring) at the Manitoba site partially due to the overestimation of available substrates for microbial denitrification from fall application during the wet spring periods. Although DNDC performed adequately for simulating most of the manure management impacts considered in this study we recommend improvements in the simulation of soil freeze-thaw cycles, manure decomposition dynamics, soil water storage, rainfall canopy interception, and microbial denitrification and nitrification activities in grasslands., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)