Author's personal copy The utility of process-based models for simulating N 2 O emissions from soils: A case study based on Costa Rican coffee plantations Kristell Hergoualc’h a, b, * , Jean-Michel Harmand a , Patrice Cannavo a,1 , Ute Skiba c , Robert Oliver d , Catherine He ´ nault e a Centre de coope ´ration International en Recherche Agronomique pour le De´veloppement (CIRAD), UR Ecosyste`mes de plantations, s/c UMR Eco&Sols (SupAgro), 2 place Viala, Ba ˆt. 12, 34060 Montpellier cedex 01, France b Departamento de Agricultura y Agroforesteria, Centro Agrono ´mico Tropical de Investigacio ´n y Ensen˜anza (CATIE), 7170 Turrialba, Costa Rica c Center of Ecology and Hydrology (CEH), Bush Estate, Penicuik EH26 0QB, Scotland, UK d Centre de coope´ration International en Recherche Agronomique pour le De ´veloppement (CIRAD), UR Risque environnemental lie´ au recyclage, TA 70/01, Av. Agropolis, 34398 Montpellier cedex 05, France e Institut National de Recherche Agronomique (INRA), UMR 1229 Microbiologie du Sol et de l’Environnement,17 rue Sully – BP 86510, 21065 Dijon Cedex, France article info Article history: Received 9 September 2008 Received in revised form 21 August 2009 Accepted 30 August 2009 Available online 12 September 2009 Keywords: Agroforestry Andosol Denitrification Heterotrophic soil respiration Inga densiflora Mineralization N 2 fixing leguminous Nitrification Water-filled pore space (WFPS) abstract Soil moisture and gaseous N-flux (N 2 O, N 2 ) dynamics in Costa Rican coffee plantations were successively simulated using a mechanistic model (PASTIS) and two process-based models (NGAS and NOE). Two fertilized (250 kg N ha 1 y 1 ) coffee plantations were considered, namely a monoculture and a system shaded by the N 2 fixing legume species Inga densiflora. In situ N 2 O fluxes were previously measured in these plantations. NGAS and NOE used specific microbial activities for the soils. To parameterize NGAS, we estimated N mineralization via in situ incubations and the contribution of heterotrophic soil respi- ration to total soil respiration. Potential denitrification rates and the proportion of denitrified N emitted as N 2 O were measured in the laboratory to define the values of NOE parameters, as well as nitrification rates and related N 2 O production rates for parameterizing both models. Soil moisture and both NGAS and NOE N 2 O fluxes were best modelled on an hourly time step. Soil moisture dynamics were satisfactorily simulated by PASTIS. Simulated N 2 O fluxes by both NGAS and NOE (3.2 and 2.1 kg N ha 1 y 1 for NGAS; 7.1 and 3.7 kg N ha 1 y 1 for NOE, for the monoculture and shaded plantations respectively) were within a factor of about 2 of the observed annual fluxes (4.3 and 5.8 kg N ha 1 y 1 , for the monoculture and shaded plantations respectively). Statistical indicators of association and coincidence between simulated and measured values were satisfactory for both models. Nevertheless, the two models differed greatly in describing the nitrification and denitrification processes. Some of the algorithms in the model NGAS were apparently not applicable to these tropical acidic Andosols. Therefore, more detailed information about microbial processes in different agroecosystems would be needed, notably if process-oriented models were to be used for testing strategies for mitigating N 2 O emissions. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Nitrous oxide (N 2 O) plays important roles in the atmosphere both as a long-lived greenhouse gas (IPCC, 2007) and by contrib- uting to the destruction of stratospheric ozone (Montzka et al., 2003). The increase in atmospheric N 2 O concentration is largely due to increased use of N fertilizer in agriculture (Stehfest and Bouwman, 2006). Coffee agriculture, which represents 7.5% of the world’s permanent crops (FAO, 2005), uses large amounts of N fertilizer (150–350 kg N ha 1 y 1 ) and can therefore be anticipated to potentially contribute significantly to increases of atmospheric N 2 O in the future. Assessment of N 2 O fluxes from agroecosystems would ideally require continuous, year-round, and spatially extensive measure- ments (Frokling et al., 1998). Unfortunately this has rarely been achieved and most in situ N 2 O studies are of relatively low temporal resolution (at best daily, but more common weekly) accompanied by corresponding soil temperature, moisture and surface NO 3  and NH 4 þ concentrations. Thus, annual N 2 O budgets are generally esti- mated by linear interpolation between measurements. There is a risk of underestimation, when N 2 O emission peaks are not * Corresponding author at: CIFOR ENV, PO box 0113 BOCBD, Bogor 16000, Indonesia. Tel.: þ62 251 8622622. E-mail address: k.hergoualch@cgiar.org (K. Hergoualc’h). 1 Present affiliation: Agrocampus Ouest Centre d’Angers, UR Environnement Physique de la plante HORticole, 2 rue Le Notre, 49045 Angers cedex 01, France. Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio 0038-0717/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.soilbio.2009.08.023 Soil Biology & Biochemistry 41 (2009) 2343–2355