Effect of agricultural practices on N2O emissions from Malagasy soils

Emissions of nitrous oxide (N20) are of concern because of the role of this gas in the greenhouse effect. The agricultural practices may affect the rate of N20 emissions from soil. The work focuses on 2 contrasted practices in use in Malagasy Highlands, i.e. a direct seeding on cover crop residues (SD) and a hand ploughing without residue return to soil (HP). Regarding potential denitrification and in situ N20 emissions, no difference was shown between both practices. Other measurements are currently in progress to confirm/invalidate this preliminary result. (Résumé d'auteur

Influence of notillage on carbon sequestration and erosion in Brazil

Les sols constituent le plus gros réservoir superficiel de C (hors les roches carbonatées), environ 1500 Gt C, ce qui équivaut à presque trois fois la quantité stockée dans la biomasse terrestre, et deux fois celle de l'atmosphère. Toute modification de l'usage des terres et, même pour les systèmes agricoles à l'équilibre, toute modification de l'itinéraire technique, peut induire des variations du stockage du carbone dans les sols. Les pratiques de labour favorisent souvent une aération du sol, qui est propice à l'activité microbienne et conduisent à une dégradation de la structure. Il en résulte sur le moyen et long terme une minéralisation accrue de la matière organique du sol. Du fait de l'absence (ou limitation) des travaux du sol (No-tillage, NT) et d'un maintien d'une couverture végétale permanente (DMC), les systèmes de semis direct favoriseraient la séquestration du carbone et limiteraient l'érosion. Au Brésil, l'apparition du semi-direct dans la Région Sud, au Paraná date du début des années 1970. Un des objectifs majeurs de l'époque était la lutte contre l'érosion, puis les recherches se sont développées vers la gestion des résidus de récolte et leur effet sur la fertilité, que ce soit pour la gestion du phosphore, le contrôle de l'acidité ou la localisation des engrais. Cette pratique, qui a pris une grande extension et continue de s'accroître dans le centre et le nord du pays, occupe actuellement entre environ 18 millions d'hectares avec une très grande diversité de milieux, d'agrosystèmes et d'itinéraires techniques. Au Brésil, la plus part des auteurs donnent des vitesses de stockage du carbone dans des sols sous semis-direct allant de 0,4 à 1,7 t C/ha/yr pour la couche 0-40 cm, avec les taux les plus élevés pour la région centrale du Cerrado. Mais certaines précautions sont nécessaires lors de la comparaison, en terme de séquestration du carbone, des systèmes de semis direct avec les systèmes labourés. Les comparaisons ne doivent pas se limiter au seul stockage de carbone dans le sol, mais doivent prendre compte les changements dans les émissions de méthane et d'oxyde nitreux qui sont des gaz à effet de serres importants. L'adoption des techniques de semis-direct s'accompagne d'une diminution des pertes en sol par érosion de l'ordre de 90% et du ruissellement superficiel de l'ordre de 70%. Ce qui évite ainsi la perte de nutriments qui sont souvent en quantité limite dans les sols du Brésil. Le succès des techniques de semis-direct au Brésil est dû historiquement au contrôle de la fertilité des sols qui est assuré surtout par la préservation de la ressource sol. Plus récemment, ce succès est amplifié par la préservation de la ressource carbone. (Résumé d'auteur

Modélisation des émissions de N2O pour deux systèmes de culture des Cerados brésiliens : comment éviter le problème des mesures discrètes ?

L'estimation des flux de N2O est un enjeu essentiel pour évaluer l'effet des pratiques culturales sur la production de gaz à effet de serre serre. La quantification in situ des flux de N2O, résultant de 2 principaux processus biologiques, nitrification et dénitrification, est délicate en raison d'une variabilité spatiale et temporelle élevée et de concentrations naturelles classiquement basses. Ce travail méthodologique vise à : (i) montrer que l'approche classique qui consiste à estimer les flux de N2O à partir de mesures quotidiennes in situ peut conduire à omettre des flux importants sur des périodes courtes (peu d'heures), (ii) caractériser les émissions potentielles de N2O du sol par nitrification et dénitrification par des mesures de laboratoire et (iii) proposer une approche par la modélisation des émissions de N2O qui évite le problème des mesures discrètes. Cette dernière approche a consisté en la combinaison de 2 modèles : un modèle mécaniste de transfert de l'eau et un modèle de simulation des émissions de N2O par nitrification et dénitrication. Deux situations agricoles tropicales de champ ont été étudiées : (i) semis direct sur couverture végétale et travail superficiel du sol sans restitution de résidus en contexte de production de riz pluvial dans les Cerrados (Brésil central) ; (ii), semis direct sur les résidus de culture et labour sans restitution de résidu au sol sur les Hautes Terres malgaches. (Résumé d'auteur

Towards an agroecological viticulture: advances and challenges

To improve its sustainability, viticulture should increase the provision of ecosystem services to decrease its use of inputs and the resulting environmental impact while maintaining high socio-economic performance. Soil functions in relation with their physical, chemical and biological properties can be regulated by proper soil surface management. Cover crops deliver ecosystem services such as protection of soils, better water infiltration and nitrogen fixation. Yet to avoid trade-off between provision of services and production of grapes, the management of cover crops should adapt to climate variations and to the yield objective. Pest and diseases can be regulated by various technical levers, including the control of the grape vegetative development. The assessment of damages due to pests and disease and of their consequences on yield losses is a key component of the design of alternative strategies of crop protection. This knowledge provides clues for designing management strategies with low pesticide use and high agro-ecological performance. A French national network of experiments has quantified the reduction of pesticide use with decision support systems, biocontrol or resistant varieties. To go further the challenge is now to design agroecological vineyards that combine innovations in management, and also in spatial organization at field, farm and landscape scales

Service crops functional markers explain soil water and nitrogen stocks at budburst in Mediterranean Vineyards. PoS1-46

In Mediterranean region, summer droughts are getting more intense with climate change, and water management is essential to avoid grapevine water and nitrogen (N) stress in order to maintain berry production (Celette and Gary 2013). Numerous studies have shown the potential of service crops for providing services in vineyards, eventually in relation to water and N supply (Garcia et al. 2018). Functional characterization is increasingly employed for cultivated ecosystems (Martin and Isaac 2015; Wood et al. 2015), with the hypothesis that functional markers could help us to predict the ecosystem services provided by cash crops and service crops (Damour et al. 2015). However, there is a lack of studies that assess the relations between functional markers and ecosystem services in field conditions. The aim of this study was to test the relations between functional markers of service crops in vineyards, and water and N stocks in soils. The experiment was carried out from 2016 to 2017 on a vineyard located in the South of France. Treatments consisted in 13 different service crop species and spontaneous vegetation in the inter-rows. Species were chosen to diversify botanical families, life cycles and growing behaviour. Service crops were sown on plots of 30m length in inter-rows. We studied plant communities of sown species and neighbouring weeds in three quadrats per treatment. At budburst, cover rate and aboveground biomass were recorded in all quadrats, and species were sort out to calculate their relative abundance. After biomass collection, soil cores were collected to measure soil water and N contents. Aboveground functional markers were measured on sown species and most frequent weeds (39 species in total) according to standardized protocols (Pérez-Harguindeguy et al. 2013). We recorded plant height, leaf area, leaf dry matter content, plant dry matter content, specific leaf area (SLA), carbon, N content and C/N ratio. Community weighted means (Garnier et al. 2004) were calculated for each marker to take into account species diversity in each quadrat. Cover rate and aboveground biomass were also included in the data analysis we performed to explain soil water and N stocks. Our results show that soil water and N stocks were related to the aboveground functional markers of the service crops and associated weeds. Different sets of markers were involved in water or N stocks relations, respectively. Among them, plant N content and C/N ratio best explained N stocks variations (28% and 19%, respectively), while most of water stock variability was explained by cover rate and total biomass (28% and 29%, respectively). These results suggest that functional characterization of service crops at plant scale is relevant to understand and predict some ecosystem services provided by service crops; however, simple indicators measured at plant community scale (e.g. cover rate and aboveground biomass) sufficiently accounts for differences in water provision at budburst

Analysis of ecosystem services trade-offs to design agroecosystems with perennial crops

Agroecosystems represent 38 % of global land use. Agroecosystems are located close to human settlements and are managed to produce food and fibers, traded in markets. Agroecosystems also produce other goods and services essential to human beings, such as climate regulation, flood mitigation, and landscape amenity. Economists and ecologists have developed the ecosystem services framework to foster the provision of these non-commercial services. Scientists can therefore help decision makers to develop sustainable ecosystems by studying ecosystem services. Here, we analyze the trade-offs of ecosystem services of farming systems. We discuss case studies of mixed perennial crops. The set of ecosystem services provided by these agroecosystems depends on their composition, structure, and management. Complex rule-based management will be required if winegrowers are to maintain an adequate set of ecosystem services across contrasting climatic years. Innovations including cover crops in banana systems can fulfill most of the objective set but will rely on increased farm labor. We then discuss the advantages, challenges, and opportunities to include the description of relations between ecosystem services in cropping system design. We propose to extend the yield gap analysis to ecosystem services, as a service gap analysis. This extension faces methodological questions about the potential provision of a service in a region. We conclude on the challenges that need to be faced if we want to use ecosystem services trade-offs to improve the contribution of agricultural systems to human well-being. (Résumé d'auteur

Anophthalmia, hearing loss, abnormal pituitary development and response to growth hormone therapy in three children with microdeletions of 14q22q23

BACKGROUND: Microdeletions of 14q22q23 have been associated with eye abnormalities and pituitary defects. Other phenotypic features in deletion carriers including hearing loss and response to growth hormone therapy are less well recognized. We studied genotype and phenotype of three newly identified children with 14q22q23 deletions, two girls and one boy with bilateral anophthalmia, and compared them with previously published deletion patients and individuals with intragenic defects in genes residing in the region. RESULTS: The three deletions were de novo and ranged in size between 5.8 and 8.9 Mb. All three children lacked one copy of the OTX2 gene and in one of them the deletion involved also the BMP4 gene. All three patients presented partial conductive hearing loss which tended to improve with age. Analysis of endocrine and growth phenotypes showed undetectable anterior pituitary, growth hormone deficiency and progressive growth retardation in all three patients. Growth hormone therapy led to partial catch-up growth in two of the three patients but just prevented further height loss in the third. CONCLUSIONS: The pituitary hypoplasia, growth hormone deficiency and growth retardation associated with 14q22q23 microdeletions are very remarkable, and the latter appears to have an atypical response to growth hormone therapy in some of the cases

Is long-term virological response related to CCR5 Delta32 deletion in HIV-1-infected patients started on highly active antiretroviral therapy?: CCR5 D32 in HIV treated patients

International audienceOBJECTIVE: The aim of the study was to determine whether the chemokine (C-C motif) receptor 5 (CCR5) Delta32 deletion is associated with long-term response to combination antiretroviral treatment (cART) in HIV-1-infected patients. METHODS: The genetic substudy of the Agence Nationale de Recherche sur le SIDA (ANRS) CO8 APROCO-COPILOTE cohort included 609 patients who started protease inhibitor-containing cART in 1997-1999. Patients were considered to have a sustained virological response if all plasma HIV RNA measurements in the period considered were <500 HIV-1 RNA copies/ml, allowing for a single blip. Virological response was compared between patients heterozygous for CCR5 Delta32 (Delta32/wt) and wild-type patients (wt/wt) from month 4 to year 3 and from month 4 to year 5. Logistic regression analysis was used to adjust for baseline demographical data, HIV RNA, CD4 cell count, antiretroviral exposure status, time spent on antiretroviral therapy at years 3 and 5 and adherence to treatment (month 4 to year 3 or 5). RESULTS: A sustained virological response was more frequent in Delta32/wt than in wt/wt patients from month 4 to year 3, with 66%vs. 52% of patients, respectively, showing a sustained response (P=0.02); after adjustment for potential confounders, the association of Delta32 with a sustained response was nearly significant (P=0.07). A sustained virological response was also more frequent in Delta32/wt patients up to year 5, with 48% showing a sustained response vs. 35% of wt/wt patients (P=0.01); after adjustment, Delta32 remained significantly associated with a sustained virological response up to year 5 (P=0.04). There was no association with CD4 response. CONCLUSION: The Delta32 deletion in Delta32/wt patients is associated with a beneficial virological response to cART in the long term. Whether this association is a direct effect of the Delta32 deletion remains unclear and requires confirmation in further observational studies