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The low nitrogen (N)-use efficiency of intensive winter oilseed rape (WOSR) cropping systems may cause negative environmental impacts, especially due to N leaching and gaseous losses. The aim of this study was to use data from field experiments (five sites across Germany representing typical WOSR regions) for parametrization of a nitrous oxide (N2O) emission component for implementation into a process-based dynamic plant-soil-atmosphere model (PSAM). After calibration and evaluation with three years of field data from five different N fertilizer treatments, a long-term simulation with 25-year historical weather data was conducted to derive functional relations and emission factors (EFs). The model performed best at higher aggregation levels (cumulative emissions over the entire cropping period, R2 of 0.48/0.77 for calibration/evaluation), but also reasonably simulated short-term dynamics (e.g., fertilizer applications, extreme weather events). Site-specific and year-specific N2O emissions varied within the range of medians from 0.56–4.93 kg N2O-N ha−1. Mineral fertilizer-induced EFs at economic optimal N inputs ranged from 0.16–0.65%, which was markedly below the aggregated IPCC standard value of 1% for direct N2O emissions. Generally, the simulated emissions were consistently higher with finer soil textures and increasing N inputs. The process-based approach, moreover, allowed the identification of the major source of N2O, which mainly originated from nitrification processes. [ABSTRACT FROM AUTHOR]

• NH 3 volatilization was measured with the Dräger Tube Method at five sites in Germany. • An adapted Plant-Soil-Atmosphere-Model (PSAM) was used to calculate site-specific N leaching. • NH 3 volatilization amounts were lower than IPCC default emission factor. • N leaching levels were site-specific depending on fertilizer amount, fertilizer type and site conditions. • Calculated indirect N 2 O emissions were 61–89% lower than default values. The aim of this study was to quantify site-specific levels of indirect nitrous oxide (N 2 O) emissions from oilseed rape (OSR) cropping in Germany, resulting from ammonia (NH 3) volatilization after organic fertilizer application and nitrate (NO 3 −) leaching based on measurement in field experiments and additional simulation modelling. In field experiments in three years (2012/13–2014/15) at five sites representing the main OSR growing areas N fertilizer amount and type of fertilizer (mineral N or digestate (DIG)) were varied. NH 3 emissions were measured after application of DIG with the Dräger Tube Method and dynamics of soil water and soil mineral nitrogen (SMN) were monitored for three years, besides other parameters influencing the N balance like plant growth. A Plant-Soil-Atmosphere-Model (PSAM) was developed from existing components to calculate site-specific N leaching. Furthermore, long term scenario analyses allowed to simulate site-specific N leaching and to analyze the impact of total N input and fertilizer N form on N uptake of OSR and the subsequent N leaching. Results showed site-specific differences in measured NH 3 emissions after DIG application ranging from 7.6 to 18.3 % of total applied N representing a lower volatilization level than the IPCC default emission factor of 20 % for organic fertilizers. PSAM was able to reproduce observed dynamics of soil water and SMN, but with site-specific accuracy. N leaching levels varied site-specifically and were dependent on fertilizer amount, fertilizer type and site conditions (weather, soil), but ranged with 5.0–17.6% also considerably below the default value of 30 % N input used by IPCC. Finally, calculated N 2 O emissions resulting from measured NH 3 volatilization was up to 61 % lower than the default value and N 2 O emissions from determined N leaching levels were 64–89% lower. [ABSTRACT FROM AUTHOR]