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Methane is a short-lived greenhouse gas (GHG) modelled distinctly from long-lived GHGs such as carbon dioxide and nitrous oxide to establish global emission budgets for climate stabilisation. The Paris Agreement requires a 24–47% reduction in global biogenic methane emissions by 2050. Separate treatment of methane in national climate policies will necessitate consideration of how global emission budgets compatible with climate stabilisation can be downscaled to national targets, but implications of different downscaling rules for national food production and climate neutrality objectives are poorly understood. This study addresses that knowledge gap by examining four methods to determine national methane quotas, and two methods of GHG aggregation (GWP100 and GWP*) across four countries with contrasting agriculture, forestry and other land use (AFOLU) sectors and socio-economic contexts (Brazil, France, India and Ireland). Implications for production of methane-intensive food (milk, meat, eggs and rice) in 2050 and national AFOLU climate neutrality targets are explored. It is assumed that methane quotas are always filled by food production where sufficient land is available. Global methane budgets for 1.5 °C scenarios are downscaled to national quotas based on: grand-parenting (equal percentage reductions across countries); equity (equal per capita emissions); ability (emission reductions proportionate to GDP); animal protein security (emissions proportionate to animal protein production in 2010). The choice of allocation method changes national methane quotas by a factor of between 1.7 (India) and 6.7 (Ireland). Despite projected reductions in emission-intensities, livestock production would need to decrease across all countries except India to comply with quotas under all but the most optimistic sustainable intensification scenarios. The extent of potential afforestation on land spared from livestock production is decisive in achieving climate neutrality. Brazil and Ireland could maintain some degree of milk and beef export whilst achieving territorial climate neutrality, but scenarios that comply with climate neutrality in India produce only circa 30% of national calorie and protein requirements via rice and livestock. The downscaling of global methane budgets into national policy targets in an equitable and internationally acceptable manner will require simultaneous consideration of the interconnected priorities of food security and (land banks available for) carbon offsetting.

This paper stemmed from a workshop 'Emerging challenges in large scale soil carbon sequestration' held in Paris on 8-10 October 2018; International audience; To respect the Paris agreement targeting a limitation of global warming below 2°C by 2100, and possibly below 1.5°C, drastic reductions of greenhouse gas emissions are mandatory but not sufficient. Large‐scale deployment of other climate mitigation strategies are also necessary. Among these, increasing soil organic carbon (SOC) stocks is an important lever because carbon in soils can be stored for long periods and land management options to achieve this already exist and have been widely tested. However, agricultural soils are also an important source of nitrous oxide (N$_2$O), a powerful greenhouse gas, and increasing SOC may influence N$_2$O emissions, likely causing an increase in many cases, thus tending to offset the climate change benefit from increased SOC storage. Here, we review the main agricultural management options for increasing SOC stocks. We evaluate the amount of SOC that can be stored as well as resulting changes in N$_2$O emissions to better estimate the climate benefits of these management options. Based on quantitative data obtained from published meta‐analyses and from our current level of understanding, we conclude that the climate mitigation induced by increased SOC storage is generally overestimated if associated N$_2$O emissions are not considered but, with the exception of reduced tillage, is never fully offset. Some options (e.g, biochar or non‐pyrogenic C amendment application) may even decrease N$_2$O emissions.; Pour respecter l'accord de Paris visant à limiter le réchauffement climatique à moins de 2°C d'ici 2100, et éventuellement à moins de 1,5°C, des réductions drastiques des émissions de gaz à effet de serre sont obligatoires mais pas suffisantes. Le déploiement à grande échelle d'autres stratégies d'atténuation du climat est également nécessaire. Parmi celles-ci, l'augmentation des stocks de carbone organique du sol (SOC) est un levier important car le carbone dans les sols peut être stocké pendant de longues périodes et les options de gestion des terres pour y parvenir existent déjà et ont été largement testées. Toutefois, les sols agricoles sont également une source importante d'oxyde nitreux (N$_2$O), un puissant gaz à effet de serre, et l'augmentation du SOC peut influer sur les émissions de N$_$O, provoquant probablement une augmentation dans de nombreux cas, tendant ainsi à compenser le bénéfice du changement climatique résultant du stockage accru du SOC. Nous passons ici en revue les principales options de gestion agricole pour l'augmentation des stocks de SOC. Nous évaluons la quantité de SOC qui peut être stockée ainsi que les changements qui en résultent dans les émissions de N$_2$O afin de mieux estimer les avantages climatiques de ces options de gestion. Sur la base des données quantitatives obtenues à partir de méta-analyses publiées et de notre niveau de compréhension actuel, nous concluons que l'atténuation du climat induite par un stockage accru du SOC est généralement surestimée si l'on ne tient pas compte des émissions de N$_2$O associées, mais, à l'exception du travail réduit du sol, n'est jamais totalement compensée. Certaines options (par exemple, le biochar ou l'application d'un amendement C non pyrogène) peuvent même réduire les émissions de N$_2$O.

By this in vitro study addressing greenhouse gas (GHG) emissions from soil-plant mesocosms, we suggest a method to investigate the joint effects of environmental conditions, growth of plants, and agricultural soil management. Soils from two long-term agricultural trials in France were placed in climate chambers. The rotation trial was with or without grain legumes, and the tillage trial used plowing or reduced tillage. Environmental conditions consisted of two contrasting temperature regimes combined with ambient (400 ppm) or high (700 ppm) CO2 concentrations in climate chambers. The plant growth went from seeding to vegetative growth. Carbon dioxide gas exchange measurements were conducted in both soil types for a period representing initial plant growth. The CO2 exchange was influenced by the growing plants increasing the mesocosm respiration and gross ecosystem production. The environmental settings had no noticeable impact on the CO2 exchange in the soils from the legume trial. The CO2 exchange from the tillage trial soils exhibited variations induced by the environmental conditions depending on the tillage treatment. The N2O emission measurements in the legume trial soils showed little variability based on rotation, however, in soils with legumes, indications that higher temperatures will lead to more N2O emission were seen.

World agriculture needs to find the right balance to cope with the trilemma between feeding a growing population, reducing its impact on biodiversity and minimizing greenhouse gas (GHG) emissions. In this paper, we evaluate a broad range of scenarios that achieve 4.3 GtCO2,eq/year GHG mitigation in the Agriculture, Forestry and Other Land-Use (AFOLU) sector by 2100. Scenarios include varying mixes of three GHG mitigation policies: second-generation biofuel production, dietary change and reforestation of pasture. We find that focusing mitigation on a single policy can lead to positive results for a single indicator of food security or biodiversity conservation, but with significant negative side effects on others. A balanced portfolio of all three mitigation policies, while not optimal for any single criterion, minimizes trade-offs by avoiding large negative effects on food security and biodiversity conservation. At the regional scale, the trade-off seen globally between biodiversity and food security is nuanced by different regional contexts.

Purpose: Soil organic carbon (SOC) plays a key role in soil functioning and in greenhouse gas exchange with the atmosphere. Land use and land use changes can critically affect SOC. However, despite various methodological developments, there is still no scientific consensus on the best method to assess the holistic impact of land use and land use change within LCA. The SOCLE project aimed to review how SOC contribution to climate change is accounted for in LCA and to test the feasibility and sensitivity of best methodological options. Methods: In total, five crop products (annual/perennial, temperate/tropical) and two livestock products were investigated through 22 scenarios of land use changes (LUC) and agricultural land management changes (LMC). Three methods were applied: IPCC Tier 1-2 (2006), Müller-Wenk and Brandaõ (2010) and Levasseur et al. (2012). We also carried out a sensitivity analysis on key variables, notably carbon stocks, reference states, and regeneration times. Results and discussion: The accounting for LUC and LMC influenced greatly the results on the climate change impact. Compared to the impact of other GHG emissions, (i) LUC impacts ranged from − 23 to + 1702% with the IPCC method and from − 5 to + 336% with the Müller-Wenk and Brandaõ method, and (ii) LMC impacts from − 130 to + 54% and from − 31 to + 11%, respectively. The sensitivity analyses stressed the critical influence of all methodological and data choices on final results. Conclusions: Based on the project results, we recommend accounting systematically for the impact of LULUC on climate change by applying, a minima, the comprehensive IPCC Tier 1 approach (2006), which provides default factors for SOC accounting. Where available, case-specific data should be used (e.g., Tier 2) for SOC stocks but also C:N ratio in order to model the degressive impact over 90% of the time period needed to reach equilibrium.

Using organic fertilizers on sugarcane mulches is a potentially interesting substitute for mineral fertilization in terms of economic and environmental impacts. However, no general agreement exists regarding the short-term effect of combining mulching and organic fertilization on greenhouse gas (GHG) emissions. Therefore, we studied different mixtures in the field by combining two amounts of sugarcane mulch (5 and 10 Mg ha−1) with different N fertilizers (urea, pig slurry, and digested sewage sludge). We measured CO2 and N2O emissions shortly after application of the mixtures (0–14 days) and the mulch decomposition dynamics from 0 to 120 days after application. We hypothesized that the relative amount of N to C modifies the decomposition dynamics and GHG fluxes. The emitted N2O-N and CO2-C were measured using static chambers. Mulch-C decomposition was measured using litterbags. Our results showed that the proportion of mulch-C remaining on the soil on day 120 was not altered by either the type of N fertilizer or the mulch amount. On a shorter time scale (0–49 days), the different N treatments affected the mulch-C and mulch-N losses and the C:N ratios, indicating a transient interaction between the dynamics of the mulch and the added N. The intensity of N2O-N emission was ranked as pig slurry > urea > digested sewage sludge, underscoring the effect of the physical form of N fertilizer. This work highlights the need to jointly study carbon and nitrogen dynamics and consider both soil carbon and gas emissions to assess the GHG balances of sugarcane farming practices.

International audience; This paper explores an original approach in which greenhouse gas (GHG) emissions and carbon (C) accumulation are assessed monthly and at landscape scale to account for the highly seasonal monsoon climate and the mobility of pastoral herds that characterize West African pastoral ecosystems. The study was conducted in northern Senegal, in the service area of the Widou Thiengoly borehole, a circular zone of 706 km(2) centered on the borehole. The C balance was calculated using an ecosystem approach, i.e. taking all main sources of GHG emissions and C sinks of the ecosystem, not only anthropogenic sources, into account. The annual C balance of the pastoral ecosystem was -0.04 +/- 0.01 tC-eq.ha(-1).year(-1), showing that total GHG emissions were mitigated by C accumulation in trees, soil and livestock. The C balance varied considerably with the seasons, with a positive monthly balance in the wet season, from July to October (+ 0.58 tC-eq.ha(-1).month(-1)) and a negative monthly balance in the cold dry season from November to February and the hot dry season from March to June (- 0.57 and -0.05 tC-eq.ha(-1).month(-1) respectively). Care should be taken when generalizing these results, which were obtained in a dry year, because of strong inter-annual variations in rainfall.

There is an urgent need for standardized monitoring of existing soil organic carbon stocks in order to accurately quantify potential negative or positive feedbacks with climate change on carbon fluxes. Given the uncertainty of flux measurements at the ecosystem scale, obtaining precise estimates of changes in soil organic carbon stocks is essential to provide an independent assessment of long-term net ecosystem carbon exchange. Here we describe the standard procedure to monitor the soil organic carbon stocks within the footprint of an eddy covariance flux tower, as applied at ecosystem stations of the Integrated Carbon Observation System. The objectives are i) to ensure comparability between sites and to be able to draw general conclusions from the results obtained across many ecosystems and ii) to optimize the sampling design in order to be able to prove changes in time using a reduced number of samples. When sampling a given site at two periods, the objective is generally to assess if changes occurred in time. The changes that can be detected (i.e., demonstrated as statistically significant) depend on several parameters such as the number of samples, the spatial sampling design, and the inherent within-site soil variability. Depending on these parameters, one can define the ‘minimum detectable change’ which is the minimum value of changed that can be statistically proved. Using simulation studies, we address the trade-off between increasing the number of samples and getting lower minimum detectable changes of soil organic carbon stocks.

Global Change Biology, 24 (5), ISSN:1354-1013, ISSN:1365-2486

Simulation models quantify the impacts on carbon (C) and nitrogen (N) cycling in grassland systems caused by changes in management practices. To support agricultural policies, it is however important to contrast the responses of alternative models, which can differ greatly in their treatment of key processes and in their response to management. We applied eight biogeochemical models at five grassland sites (in France, New Zealand, Switzerland, United Kingdom and United States) to compare the sensitivity of modelled C and N fluxes to changes in the density of grazing animals (from 100% to 50% of the original livestock densities), also in combination with decreasing N fertilization levels (reduced to zero from the initial levels). Simulated multi-model median values indicated that input reduction would lead to an increase in the C sink strength (negative net ecosystem C exchange) in intensive grazing systems: −64 ± 74 g C m−2 yr−1 (animal density reduction) and −81 ± 74 g C m−2 yr−1 (N and animal density reduction), against the baseline of −30.5 ± 69.5 g C m−2 yr−1 (LSU [livestock units] ≥ 0.76 ha−1 yr−1). Simulations also indicated a strong effect of N fertilizer reduction on N fluxes, e.g. N2O-N emissions decreased from 0.34 ± 0.22 (baseline) to 0.1 ± 0.05 g N m−2 yr−1 (no N fertilization). Simulated decline in grazing intensity had only limited impact on the N balance. The simulated pattern of enteric methane emissions was dominated by high model-to-model variability. The reduction in simulated offtake (animal intake + cut biomass) led to a doubling in net primary production per animal (increased by 11.6 ± 8.1 t C LSU−1 yr−1 across sites). The highest N2O-N intensities (N2O-N/offtake) were simulated at mown and extensively grazed arid sites. We show the possibility of using grassland models to determine sound mitigation practices while quantifying the uncertainties associated with the simulated outputs.

International audience; Covering the slurry pit has been shown to be one of the best ways to reduce ammonia emissions (NH3) during manure management. Yet, few studies have been conducted at farm scale. We studied the feasibility of three cover materials (peat, polystyrene balls and synthetic sheet roof) to reduce ammonia (NH3) emissions during on-farm storage of pig slurry. The impact on greenhouse gasemissions, methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) of covering the slurry pit was also evaluated. Simultaneous field experiments were carried out using two similar pits at a farm with peat and polystyrene ball covers, which allowed direct comparison of the feasibility ofthe two covers to reduce gas emissions (measured using the dynamic chamber technique). Emissions from the third option (using a synthetic sheet roof) were estimated by measuring the concentrations in the headspace under the cover and the air leakage from the cover with a tracer gas(CO2). Results showed that the polystyrene balls cover reduced emissions of NH3 during storage by up to 80% whatever the season, but increased potential greenhouse gas emissions by 20% in summer. No consistent reduction was achieved with the peat cover even though some individual results seemed to indicate up to 25% reduction in ammonia emissions; moreover, there was a 30%increase in CH4 and CO2 emissions during the storage period. The use of a synthetic sheet roof enabledup to 90% reduction in NH3, CH4 and CO2 emissions whatever the season.

International audience; On a previous study, the carbon footprint (CF) of all production and consumption activities of Galicia, an Autonomous Community located in the north-west of Spain, was determined and the results were used to devise strategies aimed at the reduction and mitigation of the greenhouse gas (GHG) emissions. The territorial LCA methodology was used there to perform the calculations. However, that methodology was initially designed to compute the emissions of all types of polluting substances to the environment (several thousands of substances considered in the life cycle inventories), aimed at performing complete LCA studies. This requirement implies the use of specific modelling approaches and databases that in turn raised some difficulties, i.e., need of large amounts of data (which increased gathering times), low temporal, geographical and technological representativeness of the study, lack of data, and presence of double counting issues when trying to combine the sectorial CF results into those of the total economy. In view of these of difficulties, and considering the need to focus only on GHG emissions, it seems important to improve the robustness of the CF computation while proposing a simplified methodology. This study is the result of those efforts to improve the aforementioned methodology. In addition to the territorial LCA approach, several Input-Output (IO) based alternatives have been used here to compute direct and indirect GHG emissions of all Galician production and consumption activities. The results of the different alternatives were compared and evaluated under a multi-criteria approach considering reliability, completeness, temporal and geographical correlation, applicability and consistency. Based on that, an improved and simplified methodology was proposed to determine the CF of the Galician con- sumption and production activities from a total responsibility perspective. This methodology adequately reflects the current characteristics of the Galician economy, thus increasing the representativeness of the results, and can be applied to any region in which IO tables and environmental vectors are available. This methodology could thus provide useful information in decision making processes to reduce and prevent GHG emissions.

There are many factors that influence ecosystem scale carbon, nitrogen and greenhouse gas dynamics, including the inherent heterogeneity of soils and vegetation, anthropogenic management interventions, and biotic and abiotic disturbance events. It is important therefore, to document the characteristics of the soils and vegetation and to accurately report all management activities, and disturbance events to aid the interpretation of collected data, and to determine whether the ecosystem either amplifies or mitigates climate change. This paper outlines the importance of assessing both the spatial and temporal variability of soils and vegetation and to report all management events, the import or export of C or N from the ecosystem, and the occurrence of biotic/abiotic disturbances at ecosystem stations of the Integrated Carbon Observation System, a pan-European research infrastructure.

International audience; Cover crops provide ecosystem services such as storing atmospheric carbon in soils after incorporation of their residues. Cover crops also influence soil water balance, which can be an issue in temperate climates with dry summers as for example in southern France and Europe. As a consequence, it is necessary to understand cover crops’ long-term influence on greenhouse gases (GHG) and water balances to assess their potential to mitigate climate change in arable cropping systems. We used the previously calibrated and validated soil-crop model STICS to simulate scenarios of cover crop introduction to assess their influence on rainfed and irrigated cropping systems and crop rotations distributed among five contrasted sites in southern France from 2007-2052. Our results showed that cover crops can improve mean direct GHG balance by 315 kg CO2e ha-1 yr-1 in the long term compared to that of bare soil. This was due mainly to an increase in carbon storage in the soil despite a slight increase in N2O emissions which can be compensate by adapting fertilization. Cover crops also influence the water balance by reducing mean annual drainage by 20 mm yr-1 but increasing mean annual evapotranspiration by 20 mm yr-1 compared to those of bare soil. Using cover crops to improve the GHG balance may help to mitigate climate change by decreasing CO2e emitted in cropping systems which can represent a decrease from 4.5 to 9% of annual GHG emissions of the French agriculture and forestry sector. However, if not well managed, they also could create water management issues in watersheds with shallow groundwater. Relationships between cover crop biomass and its influence on several variables such as drainage, carbon sequestration and GHG emissions could be used to extend our results to other conditions to assess the cover crops influence in a wider range of areas.

Efforts have been made in recent years to improve knowledge about soil greenhouse gas (GHG) fluxes from sub-Saharan Africa. However, data on soil GHG emissions from smallholder coffee-dairy systems have not hitherto been measured experimentally. This study aimed to quantify soil GHG emissions at different spatial and temporal scales in smallholder coffee-dairy farms in Murang'a County, Central Kenya. GHG measurements were carried out for one year, comprising two cropping seasons, using vented static chambers and gas chromatography. Sixty rectangular frames were installed on two farms comprising the three main cropping systems found in the area: 1) coffee (Coffea arabica L.); 2) Napier grass (Pennisetum purpureum); and 3) maize intercropped with beans (Zea mays and Phaseolus vulgaris). Within these fields, chambers were allocated on fertilised and unfertilised locations to capture spatial variability. Cumulative annual fluxes in coffee plots ranged from 1 to 1.9 kg N2O-N ha− 1, 6.5 to 7.6 Mg CO2-C ha− 1 and − 3.4 to − 2.2 kg CH4 -C ha− 1, with 66% to 94% of annual GHG fluxes occurring during rainy seasons. Across the farm plots, coffee received most of the N inputs and had 56% to 89% higher emissions of N2O than Napier grass, maize and beans. Within farm plots, two to six times higher emissions were found in fertilised hotspots – around the perimeter of coffee trees or within planted maize rows – than in unfertilised locations between trees, rows and planting holes. Background and induced soil N2O emissions from fertiliser and manure applications in the three cropping systems were lower than hypothesized from previous studies and empirical models. This study supplements methods and underlying data for the quantification of GHG emissions at multiple spatial and temporal scales in tropical, smallholder farming systems. Advances towards overcoming the dearth of data will facilitate the understanding of synergies and tradeoffs of climate-smart approaches for low emissions development.

Environmental impacts of livestock systems, especially pig production, have come under increasing debate in recent years. The challenge is in meeting the growing demand for food at an affordable cost, without compromising environmental integrity. Previous studies have shown that feed production is responsible for the majority of CO2-eq. emission resulting from pig farming systems. This seems to indicate that feed strategies could be an effective tool to achieve the sustainability of the pork chain. Therefore, dietary crude protein reduction, through the addition of industrial amino acids, lessens the nitrogen excretion by pigs and, consequently, could mitigate the effects on the environment of pig production. In this sense, to effectively evaluate the environmental impacts of pig production systems, life cycle assessment has been widely used in agriculture, but the effects of feed are still understudied in Brazilian conditions. Owing to the importance and the great concern in this research area, we presented in this paper an updated review focusing on the nutritional techniques and their potential to reduce the global warming potential of pig production, considering both the direct effects, related to the choice of feed ingredients and the indirect effects, related to changes in the efficiency of use of nutrient by the animals., O impacto ambiental da produção animal, especialmente da suinocultura, vêm sendo objeto de crescente debate nos últimos anos. O desafio é atender a crescente demanda por alimentos a um custo acessível, mas sem comprometer a integridade ambiental. Estudos vêm demonstrando que a produçao de rações é responsável pela maior parte das emissões de CO2-eq. do sistema de produção de suínos. Isso parece indicar que estratégias de alimentação podem ser ferramentas eficientes para alcançar a sustentabilidade da cadeia suinícola. Dessa forma, a redução do conteúdo de proteína bruta da dieta através da inclusão de aminoácidos industriais, leva à diminuição da excreção de nitrogênio em suínos e, consequentemente, pode mitigar o impacto ambiental do sistema de produção de suínos. Neste sentido, para avaliação efetiva do impacto ambiental do sistema produtivo, a análise do ciclo de vida vem sendo amplamente utilizada na agricultura, mas os efeitos da alimentação ainda são pouco estudados nas condições brasileiras. Devido a importância e a grande preocupação nesta área de pesquisa, este artigo trás uma revisão atualizada com foco nas técnicas de nutrição e principalmente no seu potencial em reduzir o potencial de aquecimento global da produção de suínos, considerando ambos os efeitos diretos, relacionados à escolha dos ingredientes da ração, e os efeitos indiretos, relacionados às mudanças na eficiência de uso de nutrientes pelos animais.

European grassland-based livestock production systems face the challenge of producing more meat and milk to meet increasing world demands and to achieve this using fewer resources. Legumes offer great potential for achieving these objectives. They have numerous features that can act together at different stages in the soil–plant–animal–atmosphere system, and these are most effective in mixed swards with a legume proportion of 30–50%. The resulting benefits include reduced dependence on fossil energy and industrial N-fertilizer, lower quantities of harmful emissions to the environment (greenhouse gases and nitrate), lower production costs, higher productivity and increased protein self-sufficiency. Some legume species offer opportunities for improving animal health with less medication, due to the presence of bioactive secondary metabolites. In addition, legumes may offer an adaptation option to rising atmospheric CO2 concentrations and climate change. Legumes generate these benefits at the level of the managed land-area unit and also at the level of the final product unit. However, legumes suffer from some limitations, and suggestions are made for future research to exploit more fully the opportunities that legumes can offer. In conclusion, the development of legume-based grassland–livestock systems undoubtedly constitutes one of the pillars for more sustainable and competitive ruminant production systems, and it can be expected that forage legumes will become more important in the future.

The objective of the work reported here was to reduce the uncertainty on the greenhouse gas balances of biofuels using agro-ecosystem modeling at a high resolution over the Ile-de-France region in Northern France. The emissions simulated during the feedstock production stage were input to a life-cycle assessment of candidate biofuel pathways: bioethanol from wheat, sugar-beet and miscanthus, and biodiesel from oilseed rape. Compared to the widely-used methodology based on fixed emission factors, ecosystem modeling lead to 55–70% lower estimates for N2O emissions, emphasizing the importance of regional factors. The life-cycle GHG emissions of first-generation biofuels were 50–70% lower than fossil-based equivalents, and 85% lower for cellulosic ethanol. When including indirect land-use change effects, GHG savings became marginal for biodiesel and wheat ethanol, but were positive due to direct effects for cellulosic ethanol.

Soil is a key compartment for climate regulation as a source of greenhouse gases (GHGs) emissions and as a sink of carbon. Thus, soil carbon sequestration strategies should be considered alongside reduction strategies for other greenhouse gas emissions. Taking this into account, several international and European policies on climate change are now acknowledging the importance of soils, which means that proper, comparable and reliable information is needed to report on carbon stocks and GHGs emissions from soil. It also implies a need for consensus on the adoption and verification of mitigation options that soil can provide. Where consensus is a key aspect, formal standards and guidelines come into play. This paper describes the existing ISO soil quality standards that can be used in this context, and calls for new ones to be developed through (international) collaboration. Available standards cover the relevant basic soil parameters including carbon and nitrogen content but do not yet consider the dynamics of those elements. Such methods have to be developed together with guidelines consistent with the scale to be investigated and the specific use of the collected data. We argue that this standardization strategy will improve the reliability of the reporting procedures and results of the different climate models that rely on soil quality data.

Climate-smart cropping systems should be designed with three objectives: reducing greenhouse gas (GHG) emissions, adapting to changing and fluctuating climate and environment, and securing food production sustainably. Agriculture can improve the net GHG emissions balance via three levers: less N2O, CH4 and CO2 emissions, more carbon storage, and green energy production (agrifuels, biogas). Reducing the application of mineral N fertilizer is the main option for reducing N2O emissions either directly or by increasing the proportion of legumes in the rotation. The most promising options for mitigating CH4 emissions in paddy fields are based on mid-season drainage or intermittent irrigation. The second option is storing more carbon in soil and biomass by promoting no-tillage (less fuel, crop residues), sowing cover crops, introducing or maintaining grasslands and promoting agroforestry. Breeding for varieties better adapted to thermal shocks and drought is mainly suggested as long-term adaptation to climate change. Short-term strategies have been identified from current practices to take advantage of more favorable growing conditions or to offset negative impacts: shifting sowing dates, changing species, cultivars and crop rotations, modifying soil management and fertilization, introducing or expanding irrigation. Some crops could also move to more suitable locations. Model-based tools and site-specific technologies should be developed to optimize, support and secure farmer's decisions in a context of uncertainty and hazards. Most of the adaptation and mitigation options are going in the same way but tradeoffs will have to be addressed (e. g. increasing the part of legumes will be possible only with significant breeding efforts). This will be a challenge for designing cropping systems in a multifunctional perspective., Des systèmes de culture climato-intelligents doivent combiner (i) réduction des émissions de gaz à effet de serre (GES), (ii) adaptation au changement et à la variabilité climatique et (iii) sécurisation de la production alimentaire. L’agriculture peut améliorer le bilan des émissions de GES via trois leviers : (i) moins d’émissions de N2O, CH4 et CO2, (ii) plus de stockage du carbone, (iii) de la production d’énergie verte (biocarburants, biogaz). Réduire l’application d’engrais minéral ou augmenter la proportion de légumineuses dans la rotation permet de réduire les émissions de N2O. La réduction des émissions de CH4 en riziculture inondée impose de revoir la gestion de l’eau (drainage, irrigation). Stocker plus de carbone dans le sol et la biomasse passe par la culture sans labour (moins d’énergie, paillage avec les résidus de récolte), l’utilisation de plantes de couverture, l’introduction ou le maintien de prairies et la pratique de l’agroforesterie. La sélection de variétés mieux adaptées aux chocs thermiques et à la sécheresse est la principale adaptation à long terme au changement climatique. Des stratégies à court terme ont été identifiées à partir des pratiques actuelles, tirant profit de conditions de croissance plus favorables ou compensant les impacts négatifs par le décalage des dates de semis, l’introduction de nouvelles espèces et cultivars, la diversification des rotations, de nouvelles pratiques de gestion du sol et de la fertilisation, l’introduction ou l’expansion de l’irrigation. Certaines cultures pourraient également migrer vers des zones de culture plus appropriées. Des outils basés sur les modèles et l’agriculture de précision devraient être développés afin d’aider les agriculteurs face à un contexte plus incertain et plus risqué. La plupart des options d’adaptation et d’atténuation sont compatibles, mais des arbitrages devront être faits : ainsi augmenter la part des légumineuses ne sera possible que si des efforts de sélection importants sont conduits.

Climate-smart approaches have gained momentum in tropical, agricultural development. However, to date, few studies have examined whole-farm greenhouse gas (GHG) balances in smallholder crop-livestock systems. This study aimed to quantify GHG balances at farm-scale, identify GHG hotspots and assess mitigation options in coffee-dairy farms undergoing agricultural intensification in Central Kenya. In recent decades, decreasing farm size has forced the shift from extensive practices to zero-grazing systems and higher nitrogen (N) inputs. We hypothesised that different farm strategies and intensification levels determine the farm’s GHG balance. A farm typology was constructed through principal component analysis (PCA) and hierarchical clustering from 125 farms surveyed. Four farm types were identified ranging relatively from small to large farms, low to high livestock intensities, and low to high N input rates. Whole-farm GHG balances were estimated using an adapted version of the Cool Farm Tool (CFT). Farms were found to be net sources of GHG, averaging from 4.5 t CO 2 eq ha −1 yr −1 in less intensive farms to 12.5 t CO 2 eq ha −1 yr −1 in high intensive farms. Within the farm GHG hotspots identified, methane (CH 4 ) from enteric fermentation processes accounted for 26–39% of total farm GHG emissions; nitrous oxide (N 2 O) and CH 4 from manure management systems (MMS) for 26–38%; soil background and fertilizer induced N 2 O emissions for 24–29%; off-farm production of feeds and agrochemicals for 10–22%; and crop residue management (CRM) for the remaining 1–3%. Within the mitigation practices assessed, zero-grazing stalls already lowered the livestock maintenance energy requirements, reducing enteric fermentation emissions. Stall-feeding, however, brings the necessity-opportunity to manage the manure and our results showed that MMS can be a determining factor in the GHG balance. Increasing the frequency of manure collection from stalls in favour of solid storage systems can reduce N 2 O emissions by up to 75%. Furthermore, dry manure storage reduced the CH 4 emissions of liquid slurry systems by more than 70%. Further benefits in terms of carbon (C) sequestration were identified along farm types from manure and crop residues applications in soils (with averages of −1.3 to −2.3 t CO 2 eq ha −1 yr −1 ) and biomass growth in agroforestry systems (−1.2 to −2 t CO 2 eq ha −1 yr −1 ). Together, soils and woody biomass offset 25–36% of farm emissions. We conclude that reduced farm size and increased livestock density lead to higher emissions per unit area, though this increase is smoothed by larger negative fluxes in soils (by higher C inputs) and woody biomass (by higher tree densities) until a steady state is reached. Average yield-scaled emissions, or product carbon footprints (CFs), resulted in 1.08 kg CO 2 eq kg coffee berry −1 , 0.64 kg CO 2 eq kg maize −1 and 1.05 kg CO 2 eq kg milk −1 on average. CFs did not always differ between farm types and intensification levels, meaning that increases in productivity were not higher than increases in GHG fluxes from intensification. This may be due to: 1) increases in productivity are the result of more processes other than N inputs; and/or 2) emissions from N inputs are overestimated by EFs and GHG calculators. Smallholders may benefit in the near future from climate initiatives and further field characterisation, models calibration and monitoring are required to overcome critical levels of uncertainty and provide more accurate estimations of GHG balances at farm-scale.

Greenhouse gas (GHG) emissions from the surface soils and surface water receiving animal excreta may be important components of the GHG balance of terrestrial ecosystems, but the associated processes are poorly documented in tropical environments, especially in tropical arid and semi-arid areas. A typical sylvo-pastoral landscape in the semi-arid zone of Senegal, West Africa, was investigated in this study. The study area (706 kmA(2) of managed pastoral land) was a circular zone with a radius of 15 km centered on a borehole used to water livestock. The landscape supports a stocking rate ranging from 0.11 to 0.39 tropical livestock units per hectare depending on the seasonal movements of the livestock. Six landscape units were investigated (land in the vicinity of the borehole, natural ponds, natural rangelands, forest plantations, settlements, and enclosed plots). Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured with static chambers set up at 13 sites covering the six landscape units, and the 13 sites are assumed to be representative of the spatial heterogeneity of the emissions. A total of 216 fluxes were measured during the one-year study period (May 2014 to April 2015). At the landscape level, soils and surface water emitted an average 19.8 t C-CO2 eq/(hm(2).a) (CO2: 82%, N2O: 15%, and CH4: 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO2 fluxes ranged from 1148.2 (+/- 91.6) mg/(m(2).d) in rangelands to 97,980.2 (+/- 14,861.7) mg/(m(2).d) in surface water in the vicinity of the borehole. N2O fluxes ranged from 0.6 (+/- 0.1) mg/(m(2).d) in forest plantations to 22.6 (+/- 10.8) mg/(m(2).d) in the vicinity of the borehole. CH4 fluxes ranged from-3.2 (+/- 0.3) mg/(m(2).d) in forest plantations to 8788.5 (+/- 2295.9) mg/(m(2).d) from surface water in the vicinity of the borehole. This study identified GHG emission "hot spots" in the landscape. Emissions from the surface soils were significantly higher in the landscape units most frequently used by the animals, i.e., in the vicinity of the borehole and settlements; and emissions measured from surface water in the vicinity of the borehole and from natural ponds were on average about 10 times higher than soil emissions.

Grâce aux avancées méthodologiques portant sur la modélisation des fonctions de production permettant la prise en compte explicite des outputs indésirables, la différenciation des fonctions-objectif des acteurs et l'agrégation sectorielle des technologies individuelles, cet article se propose d'évaluer l'éco-efficience du secteur laitier réunionnais. Cette évaluation compare deux types d'objectifs a priori opposés : les approches " productiviste " et " environnementaliste ". Selon l'approche productiviste qui souhaite maximiser la production domestique, les résultats indiquent une possible marge de progression significative de l'offre de la quantité de lait (+ 54 %) sans préjudice supplémentaire à l'environnement. Parallèlement, en privilégiant une meilleure gestion de l'environnement, l'analyse aboutit à une forte diminution possibles des quantités globales d'outputs indésirables comme les gaz à effet de serre ou les excédents d'azote (- 46 %) sans pour autant diminuer la production laitière actuelle. De façon inattendue, ces deux approches conduisent aux mêmes ordres de grandeur en termes d'indicateurs environnementaux relatifs : excédent azoté/litre de lait et gaz à effet de serre émis/litre de lait. Sur un territoire insulaire comme La Réunion, sujet aux problématiques d'autosuffisance alimentaire des départements d'outre-mer, l'analyse sectorielle de l'efficience apparait comme un outil important de décision car il permet d'analyser une allocation optimale des ressources locales et une optimisation des matières importées pour le secteur agricole.

L'évaluation de l'impact environnemental des biocarburants a été et est encore un sujet très controversé. À partir d'une synthèse bibliographique, cet article nous présente les éléments connus et les principales incertitudes concernant les enjeux environnementaux représentés par chaque génération de biocarburants.

International audience; Despite the increasing interest in assessing the greenhouse gas (GHG) budget of livestock production systems, little is known about the possible impacts of climate change on the future contribution of such systems to global warming. The aim of this study was to assess the global warming potential (GWP) of differently managed grassland-based dairy systems, based either on permanent or on sown grasslands, under climate change at two sites: Avignon (sub-arid/arid) and Mirecourt (sub-humid/humid), representative of French contrasting climates. We compared the near-past conditions (1970–1999) and projections for 2020–2049 (near future) and 2070–2099 (far future), which correspond to the SRES A2 storyline projected by the ARPEGE climate model and downscaled with quantile–quantile regionalization method. The pasture simulation model (PaSim) simulated on-site GHG emissions. Off-site emissions were assessed according to the 2006 IPCC guidelines and attributed to the corresponding grassland field under the assumption that harvested herbage is fully eaten by stalled cattle. The attributed GWP (GWPAtt) of each system was calculated by subtracting from the net C storage the N2O and CH4 emissions occurring within the grassland plot and off-site emissions resulting from farm effluents (i.e. solid and liquid manure and slurry) and the digestion and enteric fermentation by cattle of the cut herbage. Climate change was not expected to significantly modify the GWPAtt of systems, on average, but general trends were observed. Systems based on permanent grasslands presented the largest increase in GWPAtt in the far future, due to faster soil organic matter (SOM) decomposition under climate change and the additional GHG fluxes induced by increased forage production and digestion by dairy-stalled cattle. GWPAtt increase was more evident in extensively managed grassland systems conducted in humid environments (Mirecourt), with twofold higher GWPAtt. On the contrary, GWPAtt reduction is expected to be met with systems based on sown grasslands where SOM decomposition acceleration is compensated by enhanced net primary production, especially under humid conditions (Mirecourt) and for irrigated systems (with a 13% reduction of GWPAtt expressed per livestock unit day, LSU d). Although the expected reduction of the net C storage (down to 68% at Mirecourt in far future), systems based on extensive permanent grasslands will continue to be the least detrimental to global warming, with an GWPAtt of 1.2 t CO2–C eq. ha-1 year-1 and of 3.4 kg CO2–C eq. LSU-1 day-1 year-1 in the far future.

Crop residues are subjected to open burning in Indonesia. These farming practices were studied to determine the proportion of open burned and their contribution to air pollution based on crop and air pollutant specific emission factors. On an annual basis, it was estimated that 45 million tonnes of crop residues are open burned. This leads to emission of greenhouse gases and toxic pollutants. On an average, CO2 and CO dominate the overall emissions with 90% and 8% respectively. The remaining 2% are contributed by CH4, SO2, NOx, NH3, N2O, NMVOC and particulate matter. Climate charging emissions were assessed to contribute 12–14% towards global warming potential by the global crop residues open burning.

Northern peatlands cover approximately 4% of the global land surface area. Those peatlands will be particularly vulnerable to environmental and climate change and therefore it is important to investigate their total greenhouse gas (GHG) budgets, to determine the feedback on the climate. Nitrogen (N) is known to influence the GHG budget in particular by affecting the methane (CH(4)) balance. At two peatland sites in Scotland and Finland GHG fluxes of carbon dioxide (CO(2)), methane and nitrous oxide (N(2)O) and nitrogen fluxes were measured as part of the European project 'NitroEurope'. The Scottish site, Auchencorth Moss, was a GHG sink of -321, -490 and -321 g CO(2) eq m(-2) year(-1) in 2006, 2007 and 2008, respectively, with CO(2) as the dominating GHG. In contrast, the dominating GHG at the Finnish site, Lompolojankka, was CH(4), resulting in the site being a net GHG source of +485 and +431 g CO(2) eq m(-2) year(-1) in 2006 and 2007, respectively. Therefore. Auchencorth Moss had a negative global warming potential (GWP) whilst Lompolojankka had a positive GWP over the investigated time period. Initial results yielded a positive N budget for Lompolojankka of 7.1 kg N ha(-1) year(-1), meaning the site was gaining nitrogen, and a negative N budget for Auchencorth Moss of -2.4 kg N ha year(-1), meaning the site was losing nitrogen.

International audience; The objective of this study was to evaluate the effect of N fertilization and the presence of N2 fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and litterfall in two highly fertilized (250 kg N ha−1 year−1) coffee cultivation: a monoculture (CM) and a culture shaded by the N2 fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N2O emissions with 84% of the annual N2O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH4 uptakes. The higher annual N2O emissions from the shaded plantation (5.8 ± 0.3 kg N ha−1 year−1) when compared to that from the monoculture (4.3 ± 0.1 kg N ha−1 year−1) was related to the higher N input through litterfall (246 ± 16 kg N ha−1 year−1) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg−1 d.w. d−1) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha−1 year−1 and 2.2 ± 0.2 mg N kg−1 d.w. d−1). This confirms that the presence of N2 fixing shade trees can increase N2O emissions. Annual CO2 and CH4 fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO2 ha−1 year−1, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH4 ha−1 year−1, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season.

The compilation of GHG inventories has become a common practice to support environmental decision- and policy-making, for example in the context of the UNFCCC. To estimate GHG emissions, simulation models present viable alternatives to measured data. In order to make an informed decision on model selection, clear information on the purpose and applicability of a particular model is needed. This article discusses model requirements with respect to the suitability of estimating the carbon balance of dead wood and litter (dead organic matter; DOM) and soil in forests with a particular focus on policy needs under international processes such as the UNFCCC. Based on criteria established for GHG reporting under the UNFCCC including transparency, consistency, comparability, completeness and accuracy, this paper presents an approach to classify commonly used simulation models for estimating C budgets of DOM and soil in European forests. Among the six discussed models, the authors found a clear trend toward models for providing quantitatively precise, site-specific estimates. To meet reporting needs for national GHG inventories, the authors conclude that there is a need for models producing qualitative realistic and unbiased estimates at larger scales in a transparent and comparable manner. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Oil palm is the most rapidly expanding tropical perennial crop. Its cultivation raises environmental concerns, notably related to the use of nitrogen (N) fertilisers and the associated pollution and greenhouse gas emissions. While numerous and diverse models exist to estimate N losses from agriculture, very few are currently available for tropical perennial crops. Moreover, there is a lack of critical analysis of their performance in the specific context of tropical perennial cropping systems. We assessed the capacity of 11 models and 29 sub-models to estimate N losses in a typical oil palm plantation over a 25-year growth cycle, through leaching and runoff, and emissions of NH3, N2, N2O, and NOx. Estimates of total N losses were very variable, ranging from 21 to 139 kg N ha−1 yr−1. On average, 31 % of the losses occurred during the first 3 years of the cycle. Nitrate leaching accounted for about 80 % of the losses. A comprehensive Morris sensitivity analysis showed the most influential variables to be soil clay content, rooting depth, and oil palm N uptake. We also compared model estimates with published field measurements. Many challenges remain in modelling processes related to the peculiarities of perennial tropical crop systems such as oil palm more accurately.

Soil organic carbon (SOC) plays an essential function in global agroecosystems. Conservation agriculture (CA) associated with diverse and high C-input is an important tool to increase SOC, improve soil quality, and increase agronomic productivity. However, the information about the potential of highly weathered soils under CA to accumulate SOC, and when the SOC saturation may occur, is scarce. This study was based on the hypothesis that in highly weathered soil from tropical and subtropical agro-ecosystems, the potential to store SOC lies more in the sub-soil than in surface layers and is determined by nutrient scarcity. Thus, the aim of this study, performed in a long-term incubation experiment (30 months), was to: (i) assess the SOC flow and mineralization based on CO 2 -C emissions for estimating SOC accumulation; (ii) evaluate the impact of nutrient scarcity on C accumulation efficiency by soil layers; and (iii) determine when C saturation occurs in these soils. The incubation study was performed in three Brazilian Oxisols under long-term CA, and was comprised of four amounts of C-inputs (0, 6, 12 and 24 Mg C ha − 1 ) added at 0, 10 and 20-months to three soil layers (0–20, 20–40 and 40–100 cm). The CO 2 -C emission was 19.0, 9.0 and 7.0% higher in the 0–20 cm than that in 40–100 cm layer for Ponta Grossa, Londrina and Lucas do Rio Verde sites, respectively, which was associated with higher antecedent SOC content and fertility status. A higher SOC accumulation efficiency was observed for the 0–20 cm layer than in deeper layers. Nutrient scarcity in deep soil layers; especially that of P, Ca 2 + and Mg 2 + ; was the driving force limiting SOC accumulation. Carbon saturation was not achieved indicating a high SOC storage capacity in these soils. Because these and similar soils cover a large global area, they possess a large C sink to mitigate atmospheric CO 2 -C . The potential SOC storage estimated for 20–100 cm layer based on this study and upscaling for 1/3 Brazilian Oxisols (100 million ha) may offset 0.06 to 0.36 Pg C yr − 1 or 5.5% to 32.7% of the global annual greenhouse gas emissions by land use change.

International audience; AbstractIntegrated weed management aims to decrease the dependence of cropping systems on herbicides by using a combination of several agricultural practices. Environmental impacts of individual practices under various conditions are already known. However, there is scarce knowledge on the impact of combining several practices. Therefore, we studied N2O emissions of weed management cropping systems that use differing practices such as crop diversity, tillage, and herbicide pressure, during about 1 year. Data were compared with a conventionally managed cropping system. Results were also simulated using the NOE model. Results show a large variation of N2O emissions, ranging from 177 g N2O-N/ha for intensive tillage integrated weed management to 362 g N2O-N/ha for the conventional cropping system, 777 g N2O-N/ha for the no herbicide cropping system and 5226 g N2O-N/ha for no-till integrated weed management. Most N2O emissions occurred in spring, despite the absence of fertilizing related N2O peaks. The lowest emissions occurred in autumn and winter. Emissions are explained by interactions between specific soil potential denitrification rate, soil bulk density, temperature, soil water, and inorganic N contents. N2O emissions are accurately predicted by the model NOE, with a global Nash-Sutcliffe coefficient of efficiency equal to 0.80.

Nitrogen (N) losses in agroecosystems are a major environmental and economic issue. This issue is particularly pronounced in oil palm cultivation because oil palm production area is expected to increase to 12 Mha by 2050. N fertilization in oil palm plantations is mainly provided by mineral fertilizers, palm oil mill by-products, and biological fixation using legume cover crops. N loss has a major environmental impact during cultivation. For instance, 48.7 % of the greenhouse gases emitted to produce 1 t of palm oil fruit are due to N fertilization. Actually, there is little comprehensive knowledge on how to calculate N budgets in oil palm plantation in order to optimize fertilization, taking into account N leaching and N gases emissions. Here we modeled knowledge about all N fluxes in an oil palm field following standard management practices of industrial plantations, on a mineral soil, from planting to felling after a 25-year-growth cycle. The largest fluxes are internal fluxes, such as oil palm uptake, with 40–380 kg N ha−1 year−1, and the decomposition of felled palms at the end of the cycle, with 465–642 kg N ha−1. The largest losses are emissions of NH3 and leaching of NO3 −, corresponding to 0.1–42 % and 1–34 % of mineral N applied, respectively. The most uncertain and least documented fluxes are N losses such as N2O, NO x , N2 emissions, leaching, NH3 volatilization, and runoff. The most critical conditions for N losses occur during the immature phase when young palms uptake is low and during the mature phase in areas with sparse soil cover or receiving high amounts of fertilizers. Data is lacking about the effects of management practices on NO3 − leaching and N2O/NO x emissions in those critical conditions.

To explore effective ways to decrease soil CO 2 emission and increase grain yield, field experiments were conducted on two upland rice soils (Lixisols and Gleyic Luvisols) in northern Benin in West Africa. The treatments were two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mg ha −1 ) and three nitrogen fertilizers levels (no nitrogen, recommended level of nitrogen: 60 kg ha −1 , and high level of nitrogen: 120 kg ha −1 ). Potassium and phosphorus fertilizers were applied to be non-limiting at 40 kg K 2 O ha −1 and 40 kg P 2 O 5 ha −1 . Four replications of the twelve treatment combinations were arranged in a randomized complete block design. Soil CO 2 emission, soil moisture and soil temperature were measured at 5 cm depth in 6–10 days intervals during the rainy season and every two weeks during the dry season. Soil moisture was the main factor explaining the seasonal variability of soil CO 2 emission. Much larger soil CO 2 emissions were found in rainy than dry season. No-tillage significantly reduced soil CO 2 emissions compared with manual tillage. Higher soil CO 2 emissions were recorded in the mulched treatments. Soil CO 2 emissions were higher in fertilized treatments compared with non-fertilized treatments. Rice biomass and yield were not significantly different as a function of tillage systems. On the contrary, rice biomass and yield significantly increased with application of rice straw mulch and nitrogen fertilizer. The highest response of rice yield to nitrogen fertilizer addition was obtained for 60 kg N ha −1 in combination with 3 Mg ha −1 of rice straw for the two tillage systems. Soil CO 2 emission per unit grain yield was lower under no-tillage, rice straw mulch and nitrogen fertilizer treatments. No-tillage combined with rice straw mulch and 60 kg N ha −1 could be used by smallholder farmers to achieve higher grain yield and lower soil CO 2 emission in upland rice fields in northern Benin.

Composting allows simple management of animal manure but excessive aeration can increase emissions of polluting gases such as ammonia or nitrous oxide. The aim of the present work was to determine the effect of three techniques - turning, compacting and the addition of water - on gaseous emissions. One ton of cattle manure and 3 tons of turkey manure were composted in two and four cells for 46 and 51 days respectively. The manure was either turned, wetted, or compacted. Emissions of carbon dioxide, water vapor, ammonia and nitrous oxide were monitored. The results show that turning did not alter the free air space. Compacting can be used specifically to reduce the water loss. A reduction of free air space by 20-60%, either by compacting or adding water (or both), reduced the ammonia and nitrous oxide emissions by 30-70%. © 2006 Elsevier Ltd. All rights reserved.

The full greenhouse gas balance of nine contrasted grassland sites covering a major climatic gradient over Europe was measured during two complete years. The sites include a wide range of management regimes (rotational grazing, continuous grazing and mowing), the three main types of managed grasslands across Europe (sown, intensive permanent and semi-natural grassland) and contrasted nitrogen fertilizer supplies. At all sites, the net ecosystem exchange (NEE) of CO2 was assessed using the eddy covariance technique. N2O emissions were monitored using various techniques (GC-cuvette systems, automated chambers and tunable diode laser) and CH4 emissions resulting from enteric fermentation of the grazing cattle were measured in situ at four sites using the SF6 tracer method. Averaged over the two measurement years, net ecosystem exchange (NEE) results show that the nine grassland plots displayed a net sink for atmospheric CO2 of -240 +/- 70 g C m(-2) year(-1) (mean confidence interval at p > 0.95). Because of organic C exports (from cut and removed herbage) being usually greater than C imports (from manure spreading), the average C storage (net biome productivity, NBP) in the grassland plots was estimated at -104 +/- 73 g cm(-2) year(-1) that is 43% of the atmospheric CO2 sink. On average of the 2 years, the grassland plots displayed annual N2O and CH4 (from enteric fermentation by grazing cattle) emissions, in CO2-C equivalents, of 14 +/- 4.7 and 32 +/- 6.8 g CO2-C equiv. m(-2) year(-1), respectively. Hence, when expressed in CO2-C equivalents, emissions of N2O and CH4 resulted in a 19% offset of the NEE sink activity. An attributed GHG balance has been calculated by subtracting from the NBP: (i) N2O and CH4 emissions occurring within the grassland plot and (ii) off-site emissions of CO2 and CH4 as a result of the digestion and enteric fermentation by cattle of the cut herbage. On average of the nine sites, the attributed GHG balance was not significantly different from zero (-85 +/- 77 g CO2-C equiv. m(-2) year(-1)).

Adaptation and mitigation share the ultimate purpose of reducing climate change impacts. However, they tend to be considered separately in projects and policies because of their different objectives and scales. Agriculture and forestry are related to both adaptation and mitigation: they contribute to greenhouse gas emissions and removals, are vulnerable to climate variations, and form part of adaptive strategies for rural livelihoods. We assessed how climate change project design documents (PDDs) considered a joint contribution to adaptation and mitigation in forestry and agriculture in the tropics, by analyzing 201 PDDs from adaptation funds, mitigation instruments, and project standards [e.g., climate community and biodiversity (CCB)]. We analyzed whether PDDs established for one goal reported an explicit contribution to the other (i.e., whether mitigation PDDs contributed to adaptation and vice versa). We also examined whether the proposed activities or expected outcomes allowed for potential contributions to the two goals. Despite the separation between the two goals in international and national institutions, 37 % of the PDDs explicitly mentioned a contribution to the other objective, although only half of those substantiated it. In addition, most adaptation (90 %) and all mitigation PDDs could potentially report a contribution to at least partially to the other goal. Some adaptation project developers were interested in mitigation for the prospect of carbon funding, whereas mitigation project developers integrated adaptation to achieve greater long-term sustainability or to attain CCB certification. International and national institutions can provide incentives for projects to harness synergies and avoid trade-offs between adaptation and mitigation.

International audience; During composting of livestock manure, transformations of organic matter result in gaseous emissions, which can harm the environment. Two experiments were done in enclosures to measure the fluxes of NH3, N2O, CO2, CH4 and H2O emitted by 8 heaps of compost representing the range of biodegradability of nitrogen and carbon in the livestock manure. The heaps were monitored for the first 2 months, corresponding to the thermophilic phase during which nearly all-mass losses occur. Four parameters describe the NH3 emission kinetics and the main influential factors were noted: (1) the response time to reach maximum intensity is affected mainly by the initial micro-flora; (2) the amplitude depends mainly on C biodegradability and also on micro-flora; (3) the emission duration depends mainly on N biodegradability; and (4) the cumulative emission, which varied from 16.5 to 48.9% of the nitrogen initially present in the heap, depends both on C and N biodegradability. A predictive model for NH3 and CO2 emissions for the thermophilic phase of the composting of livestock manure is proposed. The variability in cumulative emissions of CO2 and of NH3 is well explained by the contents of soluble elements and hemicellulose in the dry matter (Van Soest fractioning), and soluble nitrogen (12 h extraction at 4 °C in water). In our conditions of favourable aeration and humidity, N2O and CH4 emissions were low. The role of the biodegradable carbon in reducing NH3 emission is highlighted.

About 25 m3 of a poplar bark-poultry dung mixture were composted in a covered place with natural ventilation, air entering the lower part and going out through four shafts in the upper part. The gaseous emissions were measured and analyzed. The first heap (initial C/N of 28) was monitored for one month, then turned and more dung added. The second heap (initial C/N of 8) was monitored for seven months with two intermediate turnings. For the whole experiment, N losses were estimated at 61-74% of initial N, of which 62% was lost as NH3 (38-46% of initial N) and 1% as N2O (0.6-0.7% of initial N). N-NOx losses were 1000 times lower than N-N3 H3 losses. N2O and NOx were found only at the end of the periods before the piles were turned. As for carbon, C-CO2 emissions were estimated at 45-55% of initial C content, the ratio of CH4 to CO2 in the effluent air was 1 to 100 on average, with significant variations. The global warming potential of CH and N O was estimated at respectively 25% and 50% of total CO2 emissi...

International audience; Land application of manures and slurries are a major source of pollution such as water contamination by nitrates and greenhouse gas emissions. NH3 and N2O emissions can be lowered by suitable spreading techniques. However, a comprehensive review of the impact of slurry spreading techniques is lacking. For that we developed a model, named OSEEP, that simulates the effect of slurry incorporation, slurry spatial distribution, and soil compaction on NH3 and N2O emissions. OSEEP integrates a soil compaction model, a hydraulic pedotransfer function, a NH3 volatilization model, and a crop model. We ran OSEEP for five sites in France for 7 years. Four techniques were simulated: broadcast spreading, band spreading, incorporation after surface spreading, and injection. We tested various sizes of slurry tankers and tractors. We calculated NH3 and N2O relative emissions from various spreading techniques with respect to band spreading. Results show good agreement between model calculation and published field data. We found that slurry applied by a self-propelled 15-m3 tanker with extra large tires led to an increase of 20 % in N2O emission, by comparison with a 15-m3 tanker trailed by a tractor. Hence, we show that soil compaction should be taken into account to optimize trade-offs between NH3 and N2O emissions.

In the last 40 years, the global use of mineral N fertilizers has increased to support increasing food demand. Misuse of fertilizer has led to environmental problems in some regions and the rarefaction of energy leads to an increasing cost of mineral N fertilizers. For these reasons, improving N-use efficiency of crops and cropping systems is becoming a real challenge to growers, agronomists and breeders. Nitrogen-use efficiency depends on agronomic practices including mineral and organic nitrogen fertilization and the use of legumes in cropping systems, and genetic progress in nitrogen-use efficiency. The objective of this chapter is to develop a framework of the principles governing regulation of N uptake, N allocation and growth of plants and crops, and to apply these principles in tools for improving fertilization management and breeding. A theoretical analysis of the dynamics of plant and crop N demand in relation to growth potential during the crop cycle is developed. Agronomical tools to evaluate nitrogen status of plants and crops are presented and discussed. Physiological and morphological responses of plants and crops to N deficiency are then examined. Finally, the concept of nitrogen-use efficiency is considered in the light of the principles developed previously, and avenues for improving nitrogen-use efficiency through plant breeding and agronomy are discussed from a crop physiology point of view.

This paper provides a quantitative assessment of the effects of input and output prices on French GHG emissions from agriculture, forestry and other land use (AFOLU) at the NUTS3 level. Reduced-form, random-effect spatial error models are estimated for four emissions categories (nitrogen use, manure management, enteric fermentation, and land use, land-use change and forestry) in order to account for both spatial autocorrelation and spatial unobserved heterogeneity. The main findings are: (i) price impacts on emission levels are found to be significant, although sign and magnitude vary from one emission category to the other, (ii) estimated price effects are more apparent when emission categories are analyzed separately rather than aggregated, and (iii) the spatial dimension is found to play an important role. The estimated models are then used to simulate the effects of a doubling of crop prices on AFOLU emissions. The results indicate that this would lead to an 11%-increase in agricultural sources., Cette présentation propose une évaluation quantitative des effets des prix des produits et des intrants sur les émissions française de gaz à effet de serre dues à l'agriculture, la forêt et les autres usages des sols (AFOLU) au niveau NUTS3. Plusieurs modèles (formes réduites), incluant des effets aléatoires spatiaux, sont estimés pour chacune des quatre catégories d'émissions (utilisation d'azote synthétique, gestion des effluents d'élevage, fermentation entérique et usages des sols, changements et forêts afin de tenir compte à la fois de l'auto-corrélation spatiale et de l'hétérogénéité spatiale inobservable. Les principales conclusions portent sur : (i) l'impact des prix sur les niveaux d'émission est important, bien que le signe et l'ampleur varient d'une catégorie d'émission à l'autre, (ii) les effets des prix sont plus apparents lorsque les catégories d'émissions sont analysées séparément plutôt qu'agrégées, et (iii) la dimension spatiale joue un rôle important. Les modèles estimés sont ensuite utilisées pour simuler les effets d'un doublement des prix des cultures sur les émissions AFOLU qui conduirait à une augmentation de 11% des émissions agricoles.

The Roundtable on Sustainable Palm Oil (RSPO) is a non-profit association promoting sustainable palm oil through a voluntary certification scheme. Two successive science-based working groups on greenhouse gas (GHG) were active in RSPO from 2009 to 2011, with the aim of identifying ways of achieving meaningful and verifiable reductions of GHG emissions. One of the outputs of the second group is PalmGHG, a GHG calculator using the life cycle assessment ap-proach to quantify major sources of emissions and sequestration for individual palm oil mills and their supply base. A pilot study was carried out in 2011 with nine RSPO member companies that gave an average of 1.67 t CO2e/t crude palm oil (CPO), with a range of -0.02 to +8.32t CO2e/t CPO. Previous land use and the area of peat soil used were the main causes of the variation. Further modifications to PalmGHG continue to be made in order to make the tool more flexible and comprehensive, to refine default values, and to render it more user-friendly.

Background A large proportion of the tropical rain forests of central Africa undergo periodic selective logging for timber harvesting. The REDD+ mechanism could promote less intensive logging if revenue from the additional carbon stored in the forest compensates financially for the reduced timber yield. Results Carbon stocks, and timber yields, and their associated values, were predicted at the scale of a forest concession in Gabon over a project scenario of 40 yr with reduced logging intensity. Considering that the timber contribution margin (i.e. the selling price of timber minus its production costs) varies between 10 and US$40 m −3, the minimum price of carbon that enables carbon revenues to compensate forgone timber benefits ranges between US$4.4 and US$25.9/tCO 2 depending on the management scenario implemented. Conclusions Where multiple suppliers of emission reductions compete in a REDD+ carbon market, tropical timber companies are likely to change their management practices only if very favourable conditions are met, namely if the timber contribution margin remains low enough and if alternative management practices and associated incentives are appropriately chosen.

Trans-boundary haze events in Southeast Asia are associated with large forest and peatland fires in Indonesia. These episodes of extreme air pollution usually occur during drought years induced by climate anomalies from the Pacific (El Niño Southern Oscillation) and Indian Oceans (Indian Ocean Dipole). However, in June 2013 – a non-drought year – Singapore's 24-hr Pollutants Standards Index reached an all-time record 246 (rated “very unhealthy”). Here, we show using remote sensing, rainfall records and other data, that the Indonesian fires behind the 2013 haze followed a two-month dry spell in a wetter-than-average year. These fires were short-lived (one week) and limited to a localized area in Central Sumatra (1.6% of Indonesia): burning an estimated 163,336 ha, including 137,044 ha (84%) on peat. Most burning was confined to deforested lands (82%; 133,216 ha). The greenhouse gas (GHG) emissions during this brief, localized event were considerable: 172 ± 59 Tg CO2-eq (or 31 ± 12 Tg C), representing 5–10% of Indonesia's mean annual GHG emissions for 2000–2005. Our observations show that extreme air pollution episodes in Southeast Asia are no longer restricted to drought years. We expect major haze events to be increasingly frequent because of ongoing deforestation of Indonesian peatlands.

Nitrogen (N), the most critical and essential nutrient for plant growth, largely determines the productivity in both extensive and intensive grassland systems. Nitrification and denitrification processes in the soil are the primary drivers of generating reactive N (NO3-, N2O and NO), largely responsible for N loss and degradation of grasslands. Suppressing nitrification can thus facilitate retention of soil N to sustain long-term productivity of grasslands and forage-based production systems. Certain plants can suppress soil nitrification by releasing inhibitors from roots, a phenomenon termed ‘biological nitrification inhibition’ (BNI). Recent methodological developments [e.g. bioluminescence assay to detect biological nitrification inhibitors (BNIs) from plant-root systems] led to significant advances in our ability to quantify and characterize BNI function in pasture grasses. Among grass pastures, BNI capacity is strongest in low-N environment grasses such as Brachiaria humidicola and weakest in high-N environment grasses such as Italian ryegrass (Lolium perenne) and B. brizantha. The chemical identity of some of the BNIs produced in plant tissues and released from roots has now been established and their mode of inhibitory action determined on nitrifying Nitrosomonas bacteria. Synthesis and release of BNIs is a highly regulated and localized process, triggered by the presence of NH4+ in the rhizosphere, which facilitates release of BNIs close to soil-nitrifier sites. Substantial genotypic variation is found for BNI capacity in B. humidicola, which opens the way for its genetic manipulation. Field studies suggest that Brachiaria grasses suppress nitrification and N2O emissions from soil. The potential for exploiting BNI function (from a genetic improvement and a system perspective) to develop production systems, that are low-nitrifying, low N2O-emitting, economically efficient and ecologically sustainable, is discussed.

Ongoing intensification and specialisation of livestock production lead to increasing volumes of manure to be managed, which are a source of the greenhouse gases (GHGs) methane (CH 4) and nitrous oxide (N 2O). Net emissions of CH 4 and N 2O result from a multitude of microbial activities in the manure environment. Their relative importance depends not only on manure composition and local management practices with respect to treatment, storage and field application, but also on ambient climatic conditions. The diversity of livestock production systems, and their associated manure management, is discussed on the basis of four regional cases (Sub-Saharan Africa, Southeast Asia, China and Europe) with increasing levels of intensification and priorities with respect to nutrient management and environmental regulation. GHG mitigation options for production systems based on solid and liquid manure management are then presented, and potentials for positive and negative interactions between pollutants, and between management practices, are discussed. The diversity of manure properties and environmental conditions necessitate a modelling approach for improving estimates of GHG emissions, and for predicting effects of management changes for GHG mitigation, and requirements for such a model are discussed. Finally, we briefly discuss drivers for, and barriers against, introduction of GHG mitigation measures for livestock production. There is no conflict between efforts to improve food and feed production, and efforts to reduce GHG emissions from manure management. Growth in livestock populations are projected to occur mainly in intensive production systems where, for this and other reasons, the largest potentials for GHG mitigation may be found.

The Pasture Simulation model (PaSim) was used to simulate agronomic and environmental services at 12 grassland sites in France, comparing near past climate conditions (1970–1999) and projections for near (2020–2049) and far future (2070–2099). Modelled climate change impacts were assessed using statistical and threshold-based analysis on managed (intensive, extensive) grasslands (permanent, sown), comparing shallow and deep soils, and for an ensemble of emission scenarios, climate models, and downscaling/initialization methods. Results show a significant drift of all sites towards more arid climates by the end of the century. Significant reductions in annual water drainage and herbage protein content are projected, together with new opportunities for annual and seasonal herbage production, in spring and winter especially. Simulated future conditions also show an increased interannual and seasonal variability of production. Contrary to expectations, current natural conditions reflecting large water availability are not expected to reduce future risks of negative climate change impacts on grassland systems. Notably, milk production from aftermath grazing of permanent grasslands established on deep soils at Mirecourt (humid site) is estimated to fall down below one-third of the current median value in four out of 30 years (∼13%) for 2070–2099, whereas similar shortfalls were not observed with the baseline climate. Balancing risks and opportunities, permanent extensive grasslands can be viewed as a trade-off between the continuity of grassland service provision and the mitigation of greenhouse gas emissions.

CT1 ; CT3 ; EnjS1 ; EnjS4 ; Base de données Agroclim; International audience; The results of published Life Cycle Assessments (LCAs) of biofuels are characterized by a large variability, arising from the diversity of both biofuel chains and the methodologies used to estimate inventory data. Here, we suggest that the best option to maximize the accuracy of biofuel LCA is to produce local results taking into account the local soil, climatic and agricultural management factors. Methods We focused on a case study involving the production of first-generation ethanol from sugar beet in the Picardy region in Northern France. To account for local factors, we first defined three climatic patterns according to rainfall from a 20-year series of weather data. We subsequently defined two crop rotations with sugar beet as a break crop, corresponding to current practice and an optimized management scenario, respectively. The six combinations of climate types and rotations were run with the process-based model CERES-EGC to estimate crop yields and environmental emissions. We completed the data inventory and compiled the impact assessments using Simapro v.7.1 and Ecoinvent database v2.0. Results Overall, sugar beet ethanol had lower impacts than gasoline for the abiotic depletion, global warming, ozone layer depletion and photochemical oxidation categories. In particular, it emitted between 28 % and 42 % less greenhouse gases than gasoline. Conversely, sugar beet ethanol had higher impacts than gasoline for acidification and eutrophication due to losses of reactive nitrogen in the arable field. Thus, LCA results were highly sensitive to changes in local conditions and management factors. As a result, an average impact figures for a given biofuel chain at regional or national scales may only be indicative within a large uncertainty band. Conclusions Although the crop model made it possible to take local factors into account in the life-cycle inventory, best management practices that achieved high yields while reducing environmental impacts could not be identified. Further modelling developments are necessary to better account for the effects of management practices, in particular regarding the benefits of fertiliser incorporation into the topsoil in terms of nitrogen losses abatement. Supplementary data and modelling developments also are needed to better estimate the emissions of pesticides and heavy metals in the field.

REDD+ interventions can help both people and forests adapt to climate change by conserving or enhancing biodiversity and forest ecosystem services. However, additional adaptation measures might be needed, such as the protection of agriculture and livelihoods and the development of fire management strategies. Such measures could support the sustainability of REDD+ interventions and the permanence of carbon stocks by preventing activity displacement and induced deforestation and by limiting or avoiding damage to livelihoods and ecosystems from extreme weather events. This guidebook demonstrates how community-based adaptation (CBA) can be integrated into REDD+ interventions and other mitigation activities through a 5-step approach. In addition to vulnerability analysis, a combination of participatory and analytical methods is proposed to capture the voices of multiple stakeholders at the community and broader levels and examine the linkages between adaptation interventions and REDD+. Special emphasis is placed on forest resources and forest management to explore the potential costs and benefits of adaptation interventions for effective REDD+ implementation. Case-studies from Indonesia and the Philippines demonstrate how the steps can be followed. The case study activities and the production of this guidebook were made possible by the financial contribution of the German Federal Ministry for Economic Cooperation and Development (BMZ) and the technical and logistical assistance of the Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ).