Nitrogen leaching from organic agriculture and conventinal crop rotations

The goal of our study is to investigate nitrogen leaching from organic agriculture, taking into account a complete organic rotation (6-9 years) and to compare the results with leaching from conventional systems. There are long time series on sub-root crop concentrations in conventional agriculture in the Seine Basin. These scored an average of 25 ± 4 mg N-NO3.l-1 (standard for drinking water is 11 mg N-NO3.l-1) in different types of soil, crops and climatic conditions. However, no data still exists for organic farming (OF) in this area. In 2012-2013, a total of eight practices of arable crops have been equipped with suction cups for all their rotations (5 in OF and 3 in CF), in three pedoclimatic situations, in order to determine concentrations and fluxes of nitrogen leached. In the conditions of the first step of our study, the average of sub-root concentrations in the organic rotations was 11 ± 6 mgN-NO3.l-1 (N=35) against 26 ± 9 mgN-NO3.l-1 (N=8) for the conventional ones. Organic farming in the north of France could therefore reduce by 60% the nitrogen leaching potential compared to conventional practices widely spread in the Ile-de-France Region and the Seine Basin

A vast range of opportunities for feeding the world in 2050: trade-off between diet, N contamination and international trade

International audienceThrough a detailed analysis of the FAO database, we have constructed a generalized representation of the nitrogen transfers characterizing the current agro-food system (GRAFS) of 12 macro-regions of the world in terms of functional relationships between crop farming, livestock breeding and human nutrition. Based on this model, and maintaining the current cropland areas and the performance of cropping and livestock systems in each region, we have assessed the possibilities of meeting the protein requirements of the estimated world population in 2050, according to various combinations of three critical drivers namely human diet (total amount of protein consumed and share of animal protein in this total), regional livestock production and crop fertilization intensity, in each region. The results show that feeding the projected 2050 world population would generally imply higher levels of inter-regional trade and of environmental nitrogen contamination than the current levels, but that the scenarios with less recourse to inter-regional trade generally produce less N losses to the environment. If an equitable human diet (in terms of protein consumption) is to be established globally (the same in all regions of the world), the fraction of animal protein should not exceed 40% of a total ingestion of 4 kgN capita(-1) yr(-1), or 25% of a total consumption of 5 kgN capita(-1) yr(-1). Our results show that slightly improving the agronomical performance in the most deficient regions (namely Maghreb, the Middle East, sub-Saharan Africa, and India) would make it possible not only to meet the global protein requirements with much less international trade (hence more food sovereignty), but also to reduce N environmental contamination the most efficiently

Phosphorus budget in the water-agro-food system at nested scales in two contrasted regions of the world (ASEAN-8 and EU-27)

Garnier, Josette ... et. al.-- 21 pages, 5 figures, 2 tablesPhosphorus (P) plays a strategic role in agricultural production as well as in the occurrence of freshwater and marine eutrophication episodes throughout the world. Moreover, the scarcity and uneven distribution of minable P resources is raising concerns about the sustainability of long-term exploitation. In this paper we analyze the P cycle in anthropic systems with an original multiscale approach (world region, country, and large basin scales) in two contrasting world regions representative of different trajectories in socioeconomic development for the 1961–2009 period: Europe (EU-27)/France and the Seine River Basin, and Asia (ASEAN-8)/Vietnam and the Red River Basin. Our approach highlights different trends in the agricultural and food production systems of the two regions. Whereas crop production increased until the 1980s in Europe and France and has stabilized thereafter, in ASEAN-8 and Vietnam it began to increase in the 1980s and it is still rising today. These trends are related to the increasing use of fertilizers, although in European countries the amount of fertilizers sharply decreased after the 1980s. On average, the total P delivered from rivers to the sea is 3 times higher for ASEAN-8 (300 kg P km−2 yr−1) than for EU-27 countries (100 kg P km−2 yr−1) and is twice as high in the Red River (200 kg P km−2 yr−1) than in the Seine River (110 kg P km−2 yr−1), with agricultural losses to water in ASEAN-8 3 times higher than in EU-27. Based on the P flux budgets, this study discusses early warnings and management options according to the particularities of the two world regions, newly integrating the perspective of surface water quality with agricultural issues (fertilizers, crop production, and surplus), food/feed exchanges, and diet, defining the so-called water-agro-food systemThe FIRE-FR3020 research federation is gratefully acknowledged for the organization of an interdisciplinary workshop during which the paper emerged. Estela Romero was funded by a Research Fellowship from the Iberdrola Foundation, and Najla Aissa-Grouz and Lauriane Vilmin were granted by a R2DS-Ile-de-France Region scholarshipPeer Reviewe

Émissions d’oxyde nitreux lors du traitement de l’azote des eaux usées de l’agglomération parisienne : état actuel et prévisions

La Seine, un des fleuves les plus anthropisés d’Europe, reçoit les rejets des eaux usées de près de quinze millions d’habitants, soit le quart de la population française, dont dix millions sont concentrés dans l’agglomération parisienne. Suite à la directive européenne 91/271, l’assainissement des eaux usées de l’agglomération parisienne est actuellement remodelé et amélioré. Les flux d’azote, rejetés auparavant en Seine, seront progressivement traités via des procédés basés sur des cultures libres (boues activées) ou fixées (biofiltres immergés) permettant la nitrification et la dénitrification de la pollution azotée.Néanmoins, il est désormais admis que de l’oxyde nitreux (N2O), un gaz à effet de serre destructeur de la couche d’ozone, pourrait être émis dans l’atmosphère de façon significative durant le traitement biologique de l’azote en station d’épuration (STEP). Ces émissions ont été quantifiées en fonction des charges en azote traitées et des procédés utilisés, en conditions expérimentales. En se basant sur ces résultats, nous avons évalué les émissions de N2O sur l’ensemble des stations d’épuration de l’agglomération parisienne, dans les conditions actuelles des traitements pratiqués, mais également estimé les émissions futures, suite aux principaux changements prévus aux horizons 2006-2008 et 2012-2015.Les estimations conduisent à des émissions actuelles de N2O de l’ordre de 60‑120 kg N‑N2O/j, qui augmenteront à l’issue de la première étape des travaux (2006-2008) à 320‑480 kg N‑N2O/j, pour atteindre 370‑750 kg N‑N2O/j en 2012‑2015. Les niveaux les plus bas de ces émissions pourraient être atteints si le traitement de l’azote se fait avec une oxygénation supérieure à 2 mgO2/L en nitrification et en dénitrification, avec des conditions d’anoxie totales et un ajout de méthanol permettant 100 % de la réduction de la charge en nitrate.Compte tenu de nos résultats pour les stations d’épuration (60‑120 kg N‑N2O/j) et ceux obtenus pour la Seine à l’aval du rejet des effluents non traités pour l’azote (90‑200 kg N‑N2O/j), les émissions actuelles de N2O sont estimées à 150‑320 kg N‑N2O/j, et celles du futur augmenteraient d’un facteur d’à peine 2 quand le traitement de l’azote sera complet en stations d’épuration; cette augmentation est relativement faible si l’on tient compte de la gamme de nos estimations. De plus, à l’échelle du bassin de la Seine, les émissions d’oxyde nitreux liées au traitement de l’azote dans les stations d’épuration de l’agglomération parisienne (actuel et futur) continueront de représenter une faible proportion, de 1 à 10 % par rapport aux émissions provenant des sols agricoles du bassin amont (4100‑8200 kg N‑N2O/j).The Seine, one of Europe’s rivers most affected by intense human pressures, receives wastewater discharges from almost fifteen million inhabitants, equal to a quarter of the French population, among which ten million are concentrated in the Paris conurbation. In the framework of the European directive 91/271, wastewater treatment in the Paris conurbation is being reorganized and improved. The nitrogen load, still discharged to the Seine River, will be gradually treated by fixed biological culture and activated sludge processes, allowing nitrification and denitrification of nitrogen pollution.It is now accepted that nitrous oxide (N2O), a greenhouse gas that induces the destruction of stratospheric ozone, is emitted during biological nitrogen treatment in wastewater treatment plants (WWTPs) and may be a significant source to the atmosphere. These emissions have been quantified under experimental conditions, depending on the nitrogen load treated and the treatment used. These results have allowed the estimation of N2O emissions from all WWTPs in the Paris conurbation for present treatments and also for future conditions, with new treatments being scheduled in 2006‑2008 and then in 2012‑2015.We estimate present N2O emissions to be 60‑120 kg N‑N2O/d, which would increase to 320‑480 kg N‑N2O/d in 2006‑2008 and reach 370‑750 kg N‑N2O/d in 2012‑2015. The emission levels could be limited to the lower range of values if the nitrification of nitrogen were performed at an oxygenation level higher than 2 mg O2/L and if denitrification were performed under total anoxic conditions and with a methanol addition, allowing a 100% reduction of the nitrate load.According to our results found for Paris WWTPs (60‑120 kg N‑N2O/d) and those obtained in the lower Seine River, which receives effluents not treated for nitrogen (90‑200 kg N‑N2O/d), N2O emissions amount to 150‑320 kg N‑N2O/d. This increase of N2O emissions by a factor of less than 2 is a rather low value taking into account the range of our estimates. Furthermore, at the scale of the Seine River basin, nitrous oxide emissions from nitrogen treatments in Paris conurbation WWTPs (at present or in the future) would continue to represent a low proportion, 1 to 10%, in comparison with the emissions from agricultural lands (4100‑8200 kg N‑N2O/d)

Biogeochemical budgets in three large reservoirs of the Seine basin (Marne, Seine & Aube reservoirs)

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The water-agro-food system: upscaling from the Seine river basin to the global scale

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50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland

International audienceNitrogen (N) is crucial for crop productivity. However, nowadays more than half of the N added to cropland is lost to the environment, wasting the resource, producing threats to air, water, soil and biodiversity, and generating greenhouse gas emissions. Based on FAO data, we have reconstructed the trajectory followed, in the past 50 years, by 124 countries in terms of crop yield and total nitrogen inputs to cropland (manure, synthetic fertilizer, symbiotic fixation and atmospheric deposition). During the last five decades, the response of agricultural systems to increased nitrogen fertilization has evolved differently in the different world countries. While some countries have improved their agro-environmental performances, in others the increased fertilization has produced low agronomical benefits and higher environmental losses. Our data also suggest that, in general, those countries using a higher proportion of N inputs from symbiotic N fixation rather than from synthetic fertilizer have a better N use efficiency

Carbon Dynamics Along the Seine River Network: Insight From a Coupled Estuarine/River Modeling Approach

The Seine river discharges over 700 Gg of carbon (C) every year into the sea mostly under the form of dissolved inorganic carbon (DIC) and emits 445 Gg under the form of carbon dioxide (CO2) to the atmosphere over its entire river network. The watershed, which drains 76,000 km2, is heavily populated with 18 106 inhabitants and is thus submitted to large anthropic pressure. The offline coupling of two Reactive Transport Models is used to understand the complex spatial and temporal dynamics of carbon, oxygen and nutrients and quantify the CO2 exchange at the air-water interface along the main axis of the river. The estuarine section of the Seine is simulated by the generic estuarine model C-GEM (for Carbon Generic Estuarine Model), while the upstream part of the network, devoid of tidal influence is simulated by the pyNuts-Riverstrahler modeling platform which also includes an explicit representation of the drainage network ecological functioning. Our simulations provide a process-based representation of nutrients, oxygen, total organic carbon (TOC) and the carbonate system (DIC and alkalinity) over the entire year 2010. Our coupled modeling chain allows quantifying the respective contributions of the estuarine and freshwater sections of the system in the removal of carbon as well as following the fate of TOC and DIC along the river network. Our results also allow calculating an integrated carbon budget of the Seine river network for year 2010

Development of an Open-GIS decision aid system for ecological and economical management of surface and groundwater resources in the Bistrita River Basin (Romania)

International audienceThe Bistrita River Basin (a length of 283 km, a surface of 7039 km2, a mean discharge of 65 m3/s) is one of the most important tributary of the Siret River, which is the second major affluent of the Danube River. Heavily influenced by hydraulic management and highly polluted by agricultural and urban activities in some stretches, the Bistrita river has been studied in the framework of the Diminish Project (LIFE03 ENV/ RO/000539), funded by the Life Environment Program. The project aims to support the implementation of the EU Water Framework Directive and to combat the nutrient pollution by developing an integrated, on-line, GIS-based support system for the management of the water quality in relation with human activities, using socio-economical analysis, at the scale of the river catchments. Based on modeling approaches the decisional system allows to predict which strategy will lead to the most effective reduction of nutrient concentrations within the Bistrita hydrological network and of nutrient loads transported by the Siret River into the Danube. The consequences of the nutrient pollution are discussed for two basin areas, from two points of view: i) the effects of point and diffuse pollution for surface and groundwater, on the basis of the basin response to the changing pressures over the river catchments (industrial, rural, urban, agricultural changes), ii) the economical valuation of environmental costs and cost-effectiveness of the measures, that can be proposed from socio-economic scenarios, for reaching the "good ecological status" of this river