Process‐based modeling of nitrous oxide emissions from wheat‐cropped soils at the subregional scale

Abstract

[1] Arable soils are a large source of nitrous oxide (N 2 O) emissions, making up half of the biogenic emissions worldwide. Estimating their source strength requires methods capable of capturing the spatial and temporal variability of N 2 O emissions, along with the effects of crop management. Here we applied a process-based model, Crop Environmental REsources Synthesis (CERES), with geo-referenced input data on soils, weather, and land use to map N 2 O emissions from wheat-cropped soils in three agriculturally intensive regions in France. Emissions were mostly controlled by soil type and local climate conditions, and only to a minor extent by the doses of fertilizer nitrogen applied. As a result, the direct emission factors calculated at the regional level were much smaller (ranging from 0.0007 to 0.0033 kg N 2 O-N kg À1 N) than the value of 0.0125 kg N 2 O-N kg À1 N currently recommended in the IPCC Tier 1 methodology. Regional emissions were far more sensitive to the soil microbial characteristics governing denitrification and its fraction evolved as N 2 O, soil bulk density, and soil initial inorganic N content. Mitigation measures should therefore target a reduction in the amount of soil inorganic N upon sowing of winter crops, and a decrease of the soil N 2 O production potential itself. From a general perspective, taking into account the spatial variability of soils and climate thereby appears necessary to improve the accuracy of national inventories, and to tailor mitigation strategies to regional characteristics.

Improving the accounting of field emissions in the carbon footprint of agricultural products: a comparison of default IPCC methods with readily available medium-effort modeling approaches

“…Since the Tier 2 modeling approach introduces more parameters to account for the heterogeneity of local pedo-climatic and management conditions, it is more suitable to represent field emissions at farm or project scale. Gabrielle et al (2006) also compared different modeling approaches for N 2 O emission calculation from winter wheat on regional scale. We come to the same conclusion as Gabrielle et al (2006) that in the case of fertilizer-induced field emissions, a higher Tier approach with a focus on the aforementioned regulating factors, especially regional environmental conditions, could therefore be used to adequately detect mitigation potentials.…”

Modelling the contribution of short-range atmospheric and hydrological transfers to nitrogen fluxes, budgets and indirect emissions in rural landscapes

“…-the agro-ecosystem model CERES-EGC (Gabrielle et al, 2006) is a process-based model which simulates water, carbon and nitrogen cycles in agro-ecosystems at a daily time step and at the field scale. It models vegetation growth and development, energy balance, evapotranspiration, heat and water transfer in soil above 180 cm.…”

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

“…Plot-scale models have been linked to regional databases on soil, land-use and climate to simulate emissions for boreal, temperate and wet tropical forests (e.g., Kesik et al, 2005;Werner et al, 2007), as well as for agriculturally dominated landscapes (Butterbach-Bahl et al, 2004;Gabrielle et al, 2006). However, these upscaling experiments rely heavily on the availability and quality of data on soil physical properties (e.g., Batjes, 2002) and initial conditions for soil and vegetation carbon and nitrogen stocks for model initialisation and parameterisation.…”