Epandage de matières organiques exogènes : indicateur de potentialité de stockage de carbone dans les sols et définition de classes de disponibilité d'azote

National audience

Measurement of symbiotic nitrogen fixation in the field using a multienrichment technique

International audience

Dynamics of changes in the soil organic matter, functional diversity and C and N fluxes after shift in agricultural practices of an annual crops rotation under conventional agriculture

International audience; Introduction and objectives Agricultural practices (e.g. crop rotation, tillage) lead to profound changes in soil properties, ecosystem structure (e.g. biodiversity) and functioning (e.g. ecosystem services). Whereas this has been very often characterized in the medium and long terms, little is known so far about how fast soil properties respond to changing practices at the time scale (year to several years) in which farmers take their decision in the management of their crops. In agricultural systems, increasing consideration is given to soil biodiversity, whose role has long been overlooked by agronomists, but whose preservation in now recognized as key for maintai…

Effect of timing of grassland destruction on nitrogen mineralization kinetics.

International audience

Effets des techniques culturales sans labour (TCSL) sur le stockage de carbone dans le sol

Apport de matières organiques exogènes en agriculture: indicateur de potentialité de stockage de carbone dans les sols et définition de classes de disponibilité d’azote

CT3; absent

Typology of exogenous organic matters based on chemical and biochemical composition to predict potential nitrogen mineralization

Our aim was to develop a typology predicting potential N availability of exogenous organic matters (EOMs) in soil based on their chemical characteristics. A database of 273 EOMs was constructed including analytical data of biochemical fractionation, organic C and N, and results of N mineralization during incubation of soil–EOM mixtures in controlled conditions. Multiple factor analysis and hierarchical classification were performed to gather EOMs with similar composition and N mineralization behavior. A typology was then defined using composition criteria to predict potential N mineralization. Six classes of EOM potential N mineralization in soil were defined, from high potential N minerali…

Modelling denitrification including the dynamics of denitrifiers and their progressive ability to reduce nitrous oxide: comparison with batch experiments

Nitrous oxide contributes to the global greenhouse effect and affects the chemistry of O 3 in the upper troposphere and lower stratosphere. To define a relevant model for microbial NO 3 - and N 2 O reductions in soil and estimate the parameters involved, we propose a method combining measurements of anaerobic soil slurry and simulations of NO 3 - and N 2 O reductions, including non-enzymatic competition between NO 3 - and N 2 O as electron acceptors and the microbial dynamics of two denitrifier groups that are either able or unable to reduce N 2 O. Three models varying in the description of soil capability to reduce N 2 O through denitrification were assessed. The procedure was applied on a…

Modélisation du cycle du carbone et de l'azote

International audience

Impacts des TCSL sur les gaz à effet de serre

Nitrous oxide emission by agricultural soils: a review of spatial and temporal variability for mitigation

CT3 ; EnjS4; International audience; This short review deals with soils as an important source of the greenhouse gas N2O. The production and consumption of N2O in soils mainly involve biotic processes: the anaerobic process of denitrification and the aerobic process of nitrification. The factors that significantly influence agricultural N2O emissions mainly concern the agricultural practices (N application rate, crop type, fertilizer type) and soil conditions (soil moisture, soil organic C content, soil pH and texture). Large variability of N2O fluxes is known to occur both at different spatial and temporal scales. Currently new techniques could help to improve the capture of the spatial va…

Modélisation du bilan environnemental d'une culture de colza

National audience

Isotopic fractionation due to N2 fixation in various grain legumes

National audience

Le potentiel de stockage de carbone du semis direct en comparaison d'autres techniques culturales

International audience

Modélisation du bilan environnemlental d'une culture de colza

International audience

Peaks of in situ N2O emissions are influenced by N2O producing and reducing microbial communities across arable soils

International audience; Introduction Agriculture is the main source of terrestrial N2O emissions, a potent greenhouse gas and the main cause of ozone depletion ((Hu et al., 2015). The reduction of N2O into N2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only known biological process eliminating this greenhouse gas. Recent studies showed that a previously unknown clade of N2O-reducers (nosZII) was related to the potential capacity of the soil to act as a N2O sink (see Hallin et al., 2017 and references therein). However little is known about how this group responds to different agricultural practices. Here, we investigated how N2O-producers and N2O-reducers were …

Theoretical evaluation of 15N isotopic methods for measuring symbiotic nitrogen fixation in the fied

International audience; Isotopic methods for the measurement of symbiotic N2 fixation by leguminous plants in the field rely on the use of differences in 15N enrichment between the N sources potentially available for leguminous crops, soil mineral N and atmospheric N2 . This methodology has been fully documented, especially concerning limitations due to non uniform and non constant distribution of 15N and to the use of a reference plant to measure it. Although all authors recognise the necessity of isotopic methods for giving yield independent and time-integrated estimates of symbiotic fixation, they also agree that these methods intrinsically remain imperfect. Our aim in this chapter is (i…