Papers by Jean-luc Maeght
HAL (Le Centre pour la Communication Scientifique Directe), May 18, 2015
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Tous droits réservés © Revue des sciences de l'eau, 2002 Ce document est protégé par la loi sur l... more Tous droits réservés © Revue des sciences de l'eau, 2002 Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne.
European Journal of Agronomy, May 1, 2003
Recommendations for crop management are based on agronomic diagnoses of yield determinants at plo... more Recommendations for crop management are based on agronomic diagnoses of yield determinants at plot scale usually without the farmers being involved in the evaluation process. Farmers may consequently not apply the recommendations that do not account for their own perception of yield determination. We assumed that (i) farmers have their own perceptions of yield determination; (ii) it is possible to access these perceptions through individual discussions with farmers; (iii) subsequent group discussions allow knowledge to be exchanged between farmers and a common viewpoint to be reached; (iv) agronomists can use this common viewpoint as a basis for building improved solutions in collaboration with the farmers. In this study, we used participatory methods to identify and discuss the visual references the farmers consider the crop growth as indicators to forecast the yield of their plot and the drivers they think affect these indicators. The study was conducted in two sites in the Office du Niger irrigated rice scheme in Mali and comprised three steps: (i) individual discussions with rice producers about their perception of how yield is determined, (ii) group discussions to share their individual perceptions and reach a common viewpoint, (iii) analysis of these perceptions. Seven production indicators and 29 factors that may affect these indicators were identified. The three mains indicators used by farmers were tiller abundance, hill density, and grain weight per panicle. Crop practices and constraints may prevent farmers from achieving high yields, such as a delay in the supply of fertilizers or in crop establishment. They had a complex perception of yield determination that was often close to agronomic knowledge. Here we demonstrate for the first time that farmers in the Office du Niger scheme have technical knowledge to which extension services could refer to provide relevant advice and tools for managing their constraints and improving yield.
Etude et Gestion des Sols, 1998
Les sols de la moyenne vallée du fleuve Sénégal I caractéristiques et évolution sous irrigation P... more Les sols de la moyenne vallée du fleuve Sénégal I caractéristiques et évolution sous irrigation P. Boivin(,), F. Favre(,) (2) et J-L. Maeght (2) (1) ORSTOM, Clnstitut Français de Recherche Scientifique pour le Développement en Coopération, BP 1386 Dakar (2) Ecole Polytechnique Fedérale de Lausanne, IATE-Pédologie, CH-1 O1 5 Lausanne RÉSUMÉ Les sols alluviaux de la moyenne vallée du fleuve Sénégal, développés en climat aride, sont l'objet d'aménagements hydro-agricoles visant à développer les productions irriguées. Pour l'instant, la riziculture est la production principale, complétée par du maraîchage, Ces dépôts fluviaux et fluvio-marins récents sont organisés en unités géomorphologiques. Les bourrelets de berge des multiples bras du fleuve Sénégal spnt des formations de texture argilo-sablo-limoneuse. Les cuvettes de décantation des eaux de crue sont des formations argileuses, où les sols présentent des caractères vertiques prononcés. Leur minéralogie fait apparaître un mélange de smectites et de kaolinites. De relativement mauvaises relations entre CEC et teneurs en eau laissent quelques doutes sur les proportions de minéraux à charges variables. Ces sols sont naturellement salés selon un profil descendant, hérité du passé marin récent. Les sels sont très variables en composition et sans type dominant : chlorures et sulfates pour les anions, sodium, magnésium et calcium pour les cations. Estimer leur évolution sous irrigation pose une gamme de questions très large. La modification du régime hydrique est très importante et susceptible à elle seule de créer des conditions de pédogenèse différentes. Les sels neutres d'origine marine migrent dans les profils vers la surface. Ceau du fleuve, d'influence continentale, présente une alcalinité résiduelle calcite positive, qui fait craindre une alcalinisation. Les difficultés d'approche sont nombreuses, en particulier du fait de l'absence de données anciennes, mais aussi en raison de la relative jeunesse des périmètres irrigués, et de la nécessité de diagnostiquer des évolutions complexes et encore peu marquées. Un ensemble de travaux a été conduit, pour préciser ces dynamiques et tenter de reconstituer 1'évolution du sol sous culture depuis l'aménagement. Des approches comparatives sols nus / sols cultivés ont permis de définir dans le cas des carbonates des indicateurs du fonctionnement du sol. Des suivis du fonctionnement hydro-salin des sols irrigués permettent de compléter ces approches et de définir les conditions générales d'évolution des sols en fonction de l'aménagement, de la culture et du type de sol. La faiblesse du lessivage sur les sols argileux fait craindre un processus d'alcalinisation, qui semble en cours. Les nappes superficielles sont bien drainées par le fleuve pour les sols plus perméables, mais le maraîchage qui y est généralement pratiqué ne permet pas de lessivage. Les recommandations en termes de système de culture par type de sol sont donc complexes. De nouvelles recherches nous semblent nécessaires, qui associent une approche de la géochimie des solutions, une analyse des constituants minéraux, et des essais de modélisation des transferts. Mots clés Salinité, alcalinité, Sénégal, irrigation, riziculture SUMMARY SOILS OF THE SENEGAL ßIVEß MIDDLE VALLEY: properties and evolution under irrigation The Senegal river middle valey soils, developed on alluvial deposits, are now widely concerned by irrigation projects, mainly cropped with flooded rice. The deposits are distributed in geomorphological units : mainly river banks, made of a silt, clay and sand mixture, and basins, made of clay deposits.
Effects of climate variability on shallow and deep root growth of mature rubber (Hevea brasiliens... more Effects of climate variability on shallow and deep root growth of mature rubber (Hevea brasiliensis) and teak (Tectona grandis) trees in South East Asian plantations
HAL (Le Centre pour la Communication Scientifique Directe), Mar 16, 2015
National audienceSoil erosion in farmlands is a major cause of water quality degradation and redu... more National audienceSoil erosion in farmlands is a major cause of water quality degradation and reduced crops production potential throughout the European countries. In agroforests, if the role of tree lines as physical barriers to runoffs is easily understanding, processes involving rooting systems and soil erodilbility are still unknown. Objectives-Do the presence of a tree line improve soil aggregate stability
Dégradation liée à l'accumulation de sels neutres (salinisation) Dégradation liée à l'évolution c... more Dégradation liée à l'accumulation de sels neutres (salinisation) Dégradation liée à l'évolution chimique des eaux se concentrant (alcalinisation et sodisation). Seuls les trois derniers points sont à l'étude. Les notions de salinisation, de sodisation et d'alcalinisation méritent d'être rappelées. Salinisation : il s'agit d'une accumulation de sels solubles dans le profil de sol. Si ces sels sont neutres, la principale conséquence sera un stress hydrique pour les plantes, en raison de l'augmentation de la pression osmotique. Si les sels ne sont pas neutres, la variation de pH provoquée pourra représenter un risque de dégradation ou un facteur de toxicité (ci-après). Si les sels contiennent une trop grande proportion de sodium par rapport au calcium, le sodium va s'accumuler sur le complexe d'échange des argiles : ceci s'appelle une sodisation. Lorsque le sodium représente plus de 10% du complexe d'échange, la sodisation se manifeste par une dispersion des argiles et un effondrement de la structure du sol, s'accompagnant d'une hausse du pH. Cette évolution est très dommageable pour les qualités agronomiques du sol, et la récupération d'un sol sodisé peut s'avérer difficile et coûteuse. Alcalinisation : Il s'agit d'une accumulation de bases faibles provoquant une hausse du pH. Ce risque est un risque majeur pour les sols de la vallée du fleuve Sénégal : nous en rappellerons donc le mécanisme. L'eau du fleuve Sénégal est de composition constante au cours de l'année. Elle est très peu chargée (58IlS/cm de conductivité électrique), de pH neutre (6.9 in situ) et plus riche en calcium qu'en sodium. Elle ne présente donc pas, en l'état, de risque de sodisation. Cette eau peut cependant se révéler très dangereuse. Elle est en effet légèrement excédentaire en carbonates (une base faible) (on dit alors que son alcalinité et son alcalinité résiduelle sont positives). Ce léger excédent a de lourdes conséquences si l'on tient compte du fait que l'eau se concentre par évaporation lorsque l'on irrigue. Lorsque l'eau se concentre dans les rizières, les espèces minérales en solution se concentrent également. Ceci jusqu'à ce que le produit de solubilité d'un minéral soit atteint. Le premier minéral qui précipite lorsque l'on concentre cette eau est la calcite (carbonate de calcium). Or les carbonates sont relativement plus abondants que le calcium dans l'eau. Le mécanisme de précipitation laisse donc les carbonates excédentaires en solution : le déséquilibre entre carbonates et calcium a donc été accentué. Le mécanisme de précipitation dépend du produit des concentrations en calcium et en carbonates, qui doit être constant. Puisque la teneur en carbonates a augmenté relativement à la teneur en calcium, en cas de nouvelle concentration de l'eau, une nouvelle précipitation de calcite se produira, pour une teneur de l'eau en calcium plus faible que précédemment, et une teneur en carbonates plus élevée : le phénomène s'auto-amplifie au cours du temps, et aboutit à une eau fortement déséquilibrée, riche en carbonates et donc alcaline, et très pauvre en calcium et donc sodisante. On le comprend, avec une eau de ce type, il faut impérativement éviter que le bilan hydrique soit déficitaire, il faut s'assurer au contraire qu'il y a lessivage de l'excédent de carbonates (et non accumulation résiduelle). Or aucun périmètre de la moyenne vallée ne prend réellement de précaution, faute d'avoir pris en compte ce risque. Les périmètres les mieux drainés le sont insuffisamment, et rejettent bien souvent leurs eaux dans une autre cuvette, ne faisant que déplacer le problème dans le paysage. Enfin, même en cas de drainage, les irrigations excessives pratiquées ont tendance à remonter les nappes phréatiques superficielles. Elles deviennent alors affieurantes et alimentent en permanence un flux évaporatoire qui provoque l'alcalinisation.
Context Farmland on steep slopes is increasingly abandoned because it is unsuitable for most form... more Context Farmland on steep slopes is increasingly abandoned because it is unsuitable for most forms of modern agriculture. Succession back to forest is often slow or inexistent due to over-exploitation. Observations and measurements in Dong Cao catchment 47.9 ha Vietnam, started under farming and continued after abandonment: 20 years of uninterrupted monitoring of soil, water, land use and vegetation were integrated in this study.Objective Our aim is to identify the specific combination of soil features and agricultural practices that are responsible for fast, slow or blocked succession. We differentiate between the recovery of forest structure, relatively easy, and recovery of the original species composition, more difficult.Methods Multivariate analysis of vegetation data produced plant communities in a gradient of complexity. Using classic statistics, we sought relationships between environmental variables, land use and vegetation.Results Forest recovery failed the first 10 years,...
Land uses with trees provided greater slope stability that is also less variable compared to thos... more Land uses with trees provided greater slope stability that is also less variable compared to those with shrub or herbaceous communities. Analyzing the literature, slope stability with woody vegetation was less sensitive to soil and climate factors than with herbaceous plants. To reduce risks from earthquake-and rainfall-induced landslides, the additional stabilization by trees may need to be quite high.
Geoderma, Feb 1, 2018
In many tropical regions, such as New Caledonia, soil erosion from anthropogenic activities and s... more In many tropical regions, such as New Caledonia, soil erosion from anthropogenic activities and subsequent ecological restoration are major issues that require detailed soil and vegetation data for the production of management plans. To determine if some plant species are more useful for stabilizing soil aggregates and thus reducing erodibility, we examined three species endemic to New Caledonia, and measured how root traits and associated mycorrhizas and fungi influenced Ferralsol aggregate stability (MWD). The three species are hosts to different types of mycorrhizas and were: (i) the sedge Costularia arundinacea (Sol. Ex Vahl) Kük., an AMF (arbuscular mycorrhizal fungi) host, (ii) the shrub Tristaniopsis glauca Brongn. & Gris and (iii) the tree Arillastrum gummiferum (Pancher ex Brongn. & Gris) Baill., both of the latter are ectomycorrhizal fungi (ECM) hosts. Fungal abundance, aggregate stability, soil organic carbon (SOC), iron (Fe) and aluminium (Al) sesquioxides were measured in the soil beneath 20 individuals for each species, as well as in 20 control samples of bare soil. Root functional traits including root mass density (RMD), root length density (RLD) and percentage of fine roots were measured on all individuals. Results showed that plant species can significantly influence soil aggregate stability. MWD was greater in soil beneath Costularia characterized by high RMD, RLD, percentage of fine roots and fungal abundance, while MWD in the rhizosphere of Tristaniopsis and Arillastrum was similar to that of bare soil. Fe and Al were very high in all soil samples and are suspected of masking the influence of roots, fungi and SOC on MWD at the scale of isolated ECM-hosts. Therefore, MWD alone would not be a relevant predictor of restoration on such soil and further investigations should be carried out to identify a set of predictors useful for indicating the restoration of degraded soils on ultramafic substrates.
New Phytologist, Jul 23, 2023
CABI eBooks, 2011
An account is given on: root growth and root system architecture (components and developmental pr... more An account is given on: root growth and root system architecture (components and developmental processes, root growth, tropisms and hormonal control); interactions between plant roots and the soil environment (root growth in response to soil environmental conditions, and effect of root growth and development on soil properties); and the importance of plant roots at the community scale (interactions between roots and root systems in multi-species systems, agronomic implications of multi-specific systems, and impact of root communities on climate).
Annals of Botany, Jul 6, 2016
Background Deep roots are a common trait among a wide range of plant species and biomes, and are ... more Background Deep roots are a common trait among a wide range of plant species and biomes, and are pivotal to the very existence of ecosystem services such as pedogenesis, groundwater and streamflow regulation, soil carbon sequestration and moisture content in the lower troposphere. Notwithstanding the growing realization of the functional significance of deep roots across disciplines such as soil science, agronomy, hydrology, ecophysiology or climatology, research efforts allocated to the study of deep roots remain incommensurate with those devoted to shallow roots. This is due in part to the fact that, despite technological advances, observing and measuring deep roots remains challenging. Scope Here, other reasons that explain why there are still so many fundamental unresolved questions related to deep roots are discussed. These include the fact that a number of hypotheses and models that are widely considered as verified and sufficiently robust are only partly supported by data. Evidence has accumulated that deep rooting could be a more widespread and important trait among plants than usually considered based on the share of biomass that it represents. Examples that indicate that plant roots have different structures and play different roles with respect to major biochemical cycles depending on their position within the soil profile are also examined and discussed. Conclusions Current knowledge gaps are identified and new lines of research for improving our understanding of the processes that drive deep root growth and functioning are proposed. This ultimately leads to a reflection on an alternative paradigm that could be used in the future as a unifying framework to describe and analyse deep rooting. Despite the many hurdles that pave the way to a practical understanding of deep rooting functions, it is anticipated that, in the relatively near future, increased knowledge about the deep rooting traits of a variety of plants and crops will have direct and tangible influence on how we manage natural and cultivated ecosystems.
Frontiers in Plant Science, 2013
The drivers underlying the development of deep root systems, whether genetic or environmental, ar... more The drivers underlying the development of deep root systems, whether genetic or environmental, are poorly understood but evidence has accumulated that deep rooting could be a more widespread and important trait among plants than commonly anticipated from their share of root biomass. Even though a distinct classification of "deep roots" is missing to date, deep roots provide important functions for individual plants such as nutrient and water uptake but can also shape plant communities by hydraulic lift (HL). Subterranean fauna and microbial communities are highly influenced by resources provided in the deep rhizosphere and deep roots can influence soil pedogenesis and carbon storage.Despite recent technological advances, the study of deep roots and their rhizosphere remains inherently time-consuming, technically demanding and costly, which explains why deep roots have yet to be given the attention they deserve. While state-of-the-art technologies are promising for laboratory studies involving relatively small soil volumes, they remain of limited use for the in situ observation of deep roots. Thus, basic techniques such as destructive sampling or observations at transparent interfaces with the soil (e.g., root windows) which have been known and used for decades to observe roots near the soil surface, must be adapted to the specific requirements of deep root observation. In this review, we successively address major physical, biogeochemical and ecological functions of deep roots to emphasize the significance of deep roots and to illustrate the yet limited knowledge. In the second part we describe the main methodological options to observe and measure deep roots, providing researchers interested in the field of deep root/rhizosphere studies with a comprehensive overview. Addressed methodologies are: excavations, trenches and soil coring approaches, minirhizotrons (MR), access shafts, caves and mines, and indirect approaches such as tracer-based techniques.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 26, 2012
Fine deep roots are organs of foremost functional importance and bring about evidence that teak t... more Fine deep roots are organs of foremost functional importance and bring about evidence that teak tree extracts deep water during critically dry periods. The presence of measurable amounts of deep fine roots should be taken into account when quantifying long-term carbon storage.
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Papers by Jean-luc Maeght