Euloge K. Agbossou

Bio: Euloge K. Agbossou is an academic researcher from National University of Benin. The author has contributed to research in topics: Wet season & Upland rice. The author has an hindex of 13, co-authored 68 publications receiving 531 citations.

Reducing soil CO2 emission and improving upland rice yield with no-tillage, straw mulch and nitrogen fertilization in northern Benin

Abstract: 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.

AMMA-CATCH, a Critical Zone Observatory in West Africa Monitoring a Region in Transition

Abstract: West Africa is a region in fast transition from climate, demography, and land use perspectives. In this context, the African Monsoon Multidisciplinary Analysis (AMMA)-Couplage de l'Atmosphere Tropicale et du Cycle eco-Hydrologique (CATCH) long-term regional observatory was developed to monitor the impacts of global change on the critical zone of West Africa and to better understand its current and future dynamics. The observatory is organized into three thematic axes, which drive the observation and instrumentation strategy: (i) analyze the long-term evolution of eco-hydrosystems from a regional perspective; (ii) better understand critical zone processes and their variability; and (iii) meet socioeconomic and development needs. To achieve these goals, the observatory has gathered data since 1990 from four densely instrumented mesoscale sites (similar to 10(4) km(2) each), located at different latitudes (Benin, Niger, Mali, and Senegal) so as to sample the sharp eco-climatic gradient that is characteristic of the region. Simultaneous monitoring of the vegetation cover and of various components of the water balance at these four sites has provided new insights into the seemingly paradoxical eco-hydrological changes observed in the Sahel during the last decades: groundwater recharge and/ or runoff intensification despite rainfall deficit and subsequent re-greening with still increasing runoff. Hydrological processes and the role of certain key landscape features are highlighted, as well as the importance of an appropriate description of soil and subsoil characteristics. Applications of these scientific results for sustainable development issues are proposed. Finally, detecting and attributing eco-hydrological changes and identifying possible regime shifts in the hydrologic cycle are the next challenges that need to be faced.

Barriers and opportunities for innovation in rice production in the inland valleys of Benin

Abstract: This study investigates the technical and institutional factors that hinder the effective use of irrigation water and the development of the local rice value chain in an inland valley of Benin. Primary data have been collected in three areas: Koussin-Lele, Bame and Zonmon. The diagnosis indicates that both local and higher level institutional barriers affect the development of the local rice value chain negatively. The barriers to innovation include an unclear division of responsibilities between local farmer groups and the government for canal maintenance, a lack of effective local rules for the distribution and maintenance of the irrigation infrastructure and distrust among farmers, related to privileges of the farmer leaders, as well as the constraining formal and informal credit systems and uncertain market outlets. The barriers depress rice output and the income of farmers. The windows of opportunity to stimulate innovation comprise consumers’ affinity to local products and territorial product labels, private–public community partnerships, the irrigation potential of inland valleys by the use of small pumps in combination with shallow tube well irrigation.

Combining no-tillage, rice straw mulch and nitrogen fertilizer application to increase the soil carbon balance of upland rice field in northern Benin

Abstract: Agricultural management practices are frequently non conservative and can lead to substantial loss of soil organic carbon and soil fertility, but for many regions in Africa the knowledge is very limited. To study the effect of local agricultural practices on soil organic carbon content and to explore effective ways to increase soil carbon storage, field experiments were conducted on an upland rice soil (Lixisol) in northern Benin in West Africa. The treatments comprised 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 fertilizer levels (no nitrogen, 60 kg ha ⿿1 , 120 kg ha ⿿1 ). Phosphorus and potassium fertilizers were applied to be non-limiting at 40 kg P 2 O 5 ha ⿿1 and 40 kg K 2 O ha ⿿1 per cropping season. Heterotrophic respiration was higher in manual tillage than no-tillage, and higher in mulched than in non-mulched treatments. Under the current management practices (manual tillage, with no residue and no nitrogen fertilization) in upland rice fields in northern Benin, the carbon added as aboveground biomass and root biomass was not enough to compensate for the loss of carbon from organic matter decomposition, rendering the upland rice fields as net sources of atmospheric CO 2 . With no-tillage, 3 Mg ha ⿿1 of rice straw mulch and 60 kg N ha ⿿1 , the soil carbon balance was approximately zero. With no other changes in management practices, an increase in nitrogen level from 60 kg N ha ⿿1 to 120 kg N ha ⿿1 resulted in a positive soil carbon balance. Considering the high cost of inorganic nitrogen fertilizer and the potential risk of soil and air pollution often associated with intensive fertilizer use, implementation of no-tillage combined with application of 3 Mg ha ⿿1 of rice straw mulch and 60 kg N ha ⿿1 could be recommended to the smallholder farmers to compensate for the loss of carbon from organic matter decomposition in upland rice fields in northern Benin.

Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations

Abstract: We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global scale using the machine learning technique, model tree ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5 degrees x 0.5 degrees spatial resolution and a monthly temporal resolution from 1982 to 2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were not as strong (MEf between 0.29 and 0.52). Improved accounting of disturbance and lagged environmental effects, along with improved characterization of errors in the training data set, would contribute most to further reducing uncertainties. Our global estimates of LE (158 +/- 7 J x 10(18) yr(-1)), H (164 +/- 15 J x 10(18) yr(-1)), and GPP (119 +/- 6 Pg C yr(-1)) were similar to independent estimates. Our global TER estimate (96 +/- 6 Pg C yr(-1)) was likely underestimated by 5-10%. Hot spot regions of interannual variability in carbon fluxes occurred in semiarid to semihumid regions and were controlled by moisture supply. Overall, GPP was more important to interannual variability in NEE than TER. Our empirically derived fluxes may be used for calibration and evaluation of land surface process models and for exploratory and diagnostic assessments of the biosphere.

VertigO-la revue électronique en sciences de l'environnement

Abstract: Citer cet article Bétard, F. (2015). Protection et valorisation du patrimoine géomorphologique en Île-de-France (Bassin de Paris, France) : État des lieux et perspectives. [VertigO] La revue électronique en sciences de l’environnement, 15(1). Résumé de l'article Reconnu depuis une dizaine d’années seulement, le patrimoine géomorphologique fait l’objet d’une attention accrue de la part des scientifiques et des acteurs du territoire, en raison des menaces grandissantes qui pèsent sur la préservation des reliefs et des paysages, mais aussi compte tenu des potentialités qu’offre la valorisation culturelle et touristique des sites d’intérêt géomorphologique (ou géomorphosites) pour le développement local. En France métropolitaine, la région Île-de-France concentre des enjeux forts en matière de conservation et de valorisation du patrimoine géomorphologique, surtout face à l’urbanisation croissante qui le menace directement, alors que les habitants et les visiteurs représentent un public de plus en plus demandeur pour connaître et découvrir ce nouveau type de géopatrimoine sous un angle culturel ou touristique. Cet article propose de dresser un état des lieux de la protection et de la valorisation du patrimoine géomorphologique francilien, en examinant plus particulièrement (i) les outils qui ont été utilisés jusqu’à présent pour protéger les géomorphosites remarquables de la région et (ii) les acteurs engagés dans des démarches de valorisation didactique et touristique du patrimoine géomorphologique. Des exemples choisis viennent illustrer de façon concrète les moyens qui ont été mis en oeuvre sur les géomorphosites en matière de protection, de gestion et de mise en valeur. Des perspectives sont dégagées à l’issue de cette analyse, compte tenu des inventaires en cours, des stratégies nationales de création d’aires protégées et des volontés politiques locales de mettre en valeur le patrimoine géomorphologique de leur territoire.