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Berlin Brandenburg

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  • 1
    Language: French
    In: Notes de Recherche de l'Académie d'Agriculture de France , ., 2015
    Description: Soils and associated agricultural activities are estimated to account for about 2/3 of the global emissions of nitrous oxide (N2O), a potent greenhouse gas. Soil water saturation is known to be a key factor for controlling N2O emissions. The aim of this study was to understand the controls linked to the soil hydric functioning on N2O emissions. Laboratory experiments were designed to control the hydric status of soil samples during wetting and drying cycles, and to measure simultaneously N2O fluxes (Figure 1). Three treatments of stepwise drying were performed across the range 0 to ı100 cm pressure head in two wetting–drying cycles. This experiment was reproduced for one soil sample during the acquisition of three-dimensional X-ray images. After image treatment, we could characterize the air-filled pore volume (Figures 3 and 4a) and gaseous connectivity (Figure 4b). Two types of N2O emission peaks were detected (Figure 2). A peak appeared within two or three days after rewetting and was related to microbial production processes and a slow N2O transport in water saturated soils. The second type of peak was detected within the first two steps of the decreasing pressure head, and occurred during a brief period, an average of 1.6 hour after the beginning of the soil drying. These peaks were induced by diffusion processes, and their intensities were correlated with the amount of water drained. Entrapment of N2O during the wetting phase and rapid displacement during the drying phase occurred. We highlighted the need to distinguish N2O production/consumption and transport phases to explain the variability of N2O emissions which is commonly measured.
    Description: Les sols et les activités agricoles qu’ils supportent contribueraient à environ 2/3 des émissions globales de protoxyde d’azote (N2O), un puissant gaz à effet de serre. L’objectif des travaux était la compréhension de l’influence de l’histoire hydrique des sols sur les émissions de N2O. Une expérimentation de laboratoire permettant un contrôle fin de l’état hydrique d’échantillons de sol durant des cycles de saturation et désaturation, ainsi que la mesure des flux de N2O, a été menée (Figure 1). Cette expérimentation a été reproduite pour un échantillon pendant l’acquisition simultanée d’images à l’aide d’un scanner médical à rayons X, ceci afin de caractériser le volume de pores libres à l’air (Figures 3 et 4a) et la connectivité gazeuse (Figure 4b). Deux types de pics d’émission de N2O, d’origine biologique et physique, ont été observés (Figure 2). Il a ainsi été mis en évidence la nécessité de distinguer les périodes de production/consommation de N2O de celles de son transport pour expliquer la variabilité des émissions de N2O couramment observées.
    Keywords: N2o ; Tomographie Aux Rayons X ; Saturation Du Sol ; Propriété Hydrique Du Sol ; Émission D'Azote ; Gaz À Effet De Serre ; Désaturation Du Sol ; Protoxyde D'Azote ; Milieux Et Changements Globaux ; État Hydrique
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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