Search

L’objectif de cette synthèse est de fournir un état des lieux des travaux réalisés sur le stockage decarbone organique des sols (COS) en Guadeloupe. Compte tenu des données disponibles, lesthématiques suivantes sont traitées dans ce document, après une présentation du contextebiophysique du territoire :- Déterminants des stocks de COS et spatialisation des stocks de COS ;- Evolution tendancielle des stocks de COS ;- Effet des changements d’usage des sols sur les stocks de COS ;- Effet des changements de pratiques de gestion des sols sur les stocks de COS.

L’objectif de cette synthèse est de fournir un état des lieux des travaux réalisés sur le stockage decarbone organique des sols (COS) en Martinique. Compte tenu des données disponibles, lesthématiques suivantes sont développées dans ce document, après avoir une présentation du contextebiophysique du territoire :- Déterminants des stocks de COS et spatialisation des stocks de COS ;- Effet des changements d’usage des sols sur les stocks de COS ;- Effet des changements de pratiques de gestion des sols sur les stocks de COS.

International audience; Highlights:This paper reviews ways to improve water use efficiency beyond the plant level, across time and space scales, from cells, organs, and plants, to field, farm, and landscape.Abstract:Water scarcity will be one of the main issues of the 21 st century, because of competing needs between civil, industrial, and agriculture use. While agriculture is the largest user of water, its share is bound to decrease as societies develop. Clearly, agriculture needs to become more water efficient. Improving water use efficiency (WUE) at the plant level is important although there is a long way into translating this at the farm/landscape level. As we move up from a cell/organ/plant scale to more integrated scales such as plot, field, farm system, and landscape, other factors need to be considered, including trade-offs, to possibly improve WUE. These include choices of crop variety/species, farm management, landscape design, infrastructure development, ecosystem functions, where human decisions matter. This review is a cross-disciplinary attempt to analyze ways to address WUE at these different scales where metrics of analysis are defined and trade-offs considered. The equations in this perspective paper use similar metrics across scales for an easier connection and are developed to highlight which levers, at different scales, can improve WUE. We also refer to models operating at these different scales to assess WUE. While our entry point is plants and crops, we scale up the analysis of WUE to farm systems and landscapes.

International audience; To promote greater sustainability in agriculture, development of agroecology is increasingly being invoked. What are the conditions for establishing agroecological production in tropical regions? Based upon case studies in several tropical areas, we provide here some answers to this question. We review the "pillars" (i.e. principles) and the "implementation levers" (i.e., tools) for the development of agroecology. We identify three main pillars: (1) the mobilization and management of ecological processes for the sustainable production and the resilience of agroecosystems; (2) the development of interactions between technical, social, environmental, and institutional components of agroecosystems for a holistic approach to agroecology; and (3) the scaling up of agroecology that takes place with a plurality of actions and pathways at different organization levels rather than an increase in resources and a replication of standardized technical processes. To implement these three pillars, we identify 11 main biotechnical, cognitive, socio-political, and organizational levers. Bio-technical levers include those for (1) mobilizing complementarity between crop species to optimize natural resources use, (2) mobilizing functional biodiversity at the plot scale to optimize natural regulation of pests and diseases, (3) managing biodiversity at landscape and territorial scales, (4) increasing the efficiency of biogeochemical cycles, and (5) renewing targets for genetic improvement. Cognitive, socio-political, and organizational levers include those for (6) political and institutional action at the national and global level, (7) action at the local level to support producers, (8) political and organizational action at the territorial level, (9) the marketing and the development of new agri-chains, (10) the development of new methods for evaluating production systems, and (11) the recognition of the values of gender and generation within families and other organisational levels. This paper provides an overall orientation for the agroecological transition in tropical agriculture and also considers the socio-political context that underlies this transition.

International audience; L’Inde a connu en 2021 le plus grand mouvement social paysan de son histoire. Celui-ci a réussi à s’opposer, avec succès, aux réformes libérales du marché agricole voulues par le gouvernement Modi. Si cette mobilisation se situe dans la droite ligne de la défense des intérêts de la petite paysannerie contre l’agro-industrie, elle ne manifeste par contre guere d’appétence pour un changement de modèle productif et une transition agroécologique. Analysant les raisons de cette dichotomie, Frédéric Landy et Bruno Dorin explorent, en partant de l’expérience de l’Andhra Pradesh, le rôle que les États locaux peuvent jouer pour faire gagner l’agroécologie.

L'adaptation des cultures fruitières à leur environnement pédoclimatique est un phénomène qui ne peut s'analyser que sur le long terme. Elle conditionne étroite-ment la répartition géographique des espèces à l'échelle mondiale comme au sein d'un même pays ou d'une région. La répartition géographique actuelle a contribué à cristalliser la présence d'entreprises de production et de transformation, qui à leur tour ont participé au façonnement des territoires et de leur histoire. Dans le contexte du changement climatique en cours, l'ampleur et la nature des capacités d'adaptation des cultures fruitières sont donc des questionnements majeurs pour l'ensemble des agents économiques (producteurs, industries agroalimentaires ou d'agro-fournitures) qui, au sein d'un territoire donné, sont impliqués dans ces filières. Ces capacités d'adaptation sont également une source de réflexions sur les opportunités que le changement climatique pourrait procurer. Ainsi, pour prendre l'exemple du pommier, espèce fruitière mondialement cultivée, il est classique de considérer qu'il est bien adapté au climat tempéré. C'est en effet entre les 30 e et 50 e parallèles des hémisphères Nord et Sud que l'on trouve les plus grandes aires de production et de transformation de la pomme. Au-delà de ces latitudes , les risques plus élevés de gels nocturnes et la faible longueur de la saison de végétation constituent les freins majeurs à une culture commercialement rentable. En deçà, dans la région intertropicale, c'est essentiellement une insuffisance de températures froides en automne et en hiver qui limite une bonne croissance et floraison du pommier (Barden et Neilsen, 2003). Cependant, des travaux, parfois anciens, montrent qu'une exploration plus approfondie des capacités d'adaptation pourrait permettre de dépasser ces règles générales. Ainsi, la variabilité génétique au sein des espèces cultivées en régions climatiques tempérées doit être mieux analysée pour être valorisée (voir chapitre 11). Les programmes de sélection de divers arbres fruitiers tempérés au Brésil (Pommer et Barbosa, 2009) ou du pêcher aux États-Unis, particulièrement en Floride (Lyrene, 2005), montrent l'intérêt d'intégrer ces critères d'adaptation au climat dans les schémas de sélection.

International audience; Highlights:• Cocoa-based agroforestry systems were co-designed to increase their productivity and generated income.• Various participative tools were combined in an original co-design approach.• Innovations focused on diversity, density and spatial arrangement of crop species.• This co-design method is generic and can be applied to other complex systems.Abstract: Farmers constantly adapt cropping systems to meet their needs. Cocoa farming is frequently associated with low incomes and little access to technical innovations for the small farmers and their families who are responsible for most cocoa production around the world. A collaborative approach, including different professionals working in the Dominican cocoa sector, led to the emergence of many technical innovations designed to modify the current agroforestry systems (AFS) in order to increase their overall productivity while maintaining a high level of biodiversity. Two types of original results are presented: (i) the co-design method that combined different participatory tools drawn from the literature and (ii) the results of applying the method for the co-design of complex AFS in four working groups. Compared to current AFS, a first level of innovation that emerged during the workshops involves the diversity and density of associated crops in AFS. The second level of innovation deals with the evolution over time and location of the different species selected for the AFS plots. This participatory work led to the formulation of four AFS prototypes whose crop species and densities follow spatio-temporal dynamics anticipated to be capable of providing better revenues while maintaining a high level of crop biodiversity. The different technical and management innovations of these prototypes are described and discussed. The AFS prototypes resulting from the co-design process will be established on farm to assess their agronomic, ecological and economic performances.

International audience; Highlights:• The diversity of oil palm smallholders management practice and their performances remain poorly known.• We aim to understand which farming systems optimize the economic performance of oil palm.• A first typology on agricultural practices revealed a gradient of intensification, a second on economic performances revealed an optimum.• Crossing the two typologies showed that intensive practices are not economically optimal.• The study recommends to adapt local recommendations using multicriteria approaches.Abstract:CONTEXT: Oil palm is widely cultivated in Indonesia and it is produced by various populations of smallholders. Among those, ex-plasma smallholders are characterized by the fact that they only start to manage their own plantations 5 to 10 years after those were initially planted and managed by a partner industrial company. Despite the large areas that are cultivated by ex-plasma smallholders, their diversity of practices and economic performances are poorly quantified.OBJECTIVE: The present study aims at investigating which smallholder farming systems optimize profitability at the plot scale.METHOD: We defined two typologies, one based on agricultural practices and the other based on economic performance, using multivariate statistical analysis. The typologies were crossed to understand the links between agricultural practices and economic performance at the plot level.RESULTS AND CONCLUSIONS: Our results showed that despite initial plot homogeneity during planting phase, ex-plasma smallholders can develop very diversified management practices. A gradient of intensification was observed from farmers implementing no fertilization or weeding management up to farmers following agroindustrial-like management. Economic performances at the plot level was found to be variable, with gross margins ranging from 1.1 to 26.9 M IDR.ha−1.yr−1 (eq. 66.4 to 1625.5€). We showed that the most intensive practices led to highest yields although these were not linked to the optimal economic plot performances. A trade-off based on input costs was revealed, as high fertilization practices did not seem economically optimal for smallholders.SIGNIFICANCE: The present study highlights the need to combine quantified agronomic assessments with economic analysis, to properly design recommendations to farmers.

International audience; Lengthening and diversifying crop rotations is an efficient strategy to reduce the use of fertilizers and pesticides, thereby improving the sustainability of cropping systems. To test this assumption, six innovative cropping system prototypes were designed, each introducing one or more agroecological practices, as alternatives to the 2-year sunflower (Helianthus annuus L.)-durum wheat (Triticum turgidum L. subsp. durum) rotation widespread in southwestern France. Two 3-year rotations were implemented at INRAE, Toulouse, from 2011 to 2016. The six prototypes were composed of two low-input cropping systems (with/without cover crops) and four very low-input cropping systems (including cultivar or species mixtures, each with/without cover crops). As compared to the sunflower-wheat rotation, the prototypes aimed at reducing the use of N fertilizers by 25% (low-input) and 50% (very low-input) and pesticides by 50%. A set of agronomic, environmental, technical, and socio-economic indicators was calculated to assess the different components of sustainability. The introduction of agroecological principles resulted in a clear reduction of the use of synthetic inputs as compared to the sunflower-wheat rotation. The treatment frequency index was decreased by 56, 18 and 39% for the low-input cropping systems, very low-input cropping systems with cultivar mixtures, and very low-input cropping systems with species mixtures, respectively. However, the profitability decreased with the diversification of cropping systems as the semi-net margin decreased for the three previous cropping systems (745, 696, and 438 euro center dot ha(-1), respectively, vs. 963 euro center dot ha(-1) for the sunflower-wheat rotation). Despite the costs of inputs, the short rotation remained the most profitable. Agroecological practices succeeded in reducing the dependence of cropping systems on synthetic inputs, but their implementation needs to be improved to achieve better economic performance, using both scientific knowledge and know-how of innovative farmers.

International audience; Plant diversification is one of the main ways to ecologically intensify agroecosystems to improve their sustainability and resilience. Rotations and/or a mixture of crops can mitigate pest and weed infestation, reduce diseases, and improve soil fertility and crop productivity. However, rainfed rice yields in the Malagasy highlands remain low despite the frequent use of cropping systems including crop rotations and mixtures. In this study, we compared three rainfed rice based short rotations with rainfed rice monocropping to quantify the benefits of plant diversification on different ecosystem functions such as weed and nematode control, soil fertility, soil macrofauna abundance and diversity, and rice yield over four cropping seasons. The three rotations were based on rice in rotation with one legume, groundnut (RG), a cereal-legume mixture, sorghum and cowpea (RSC), or a mixture of legumes, velvet bean and crotalaria (RVC). Rice growth, N content and yield, soil N content, weed biomass, nematofauna and macrofauna were assessed and a profitability analysis was performed at rotation scale. The legume mixture had a significant and positive effect on rice growth, N content and yield, soil N content, and weed and nematode control due to high biomass production in the cropping cycle including legume mixture, by limiting weed growth and leaving a large quantity of N-rich residues to enrich the soil for the following rice crop. The nematicide properties of the legume mixture may reduce the infestation of plant-feeding nematodes. The RG and RSC rotations produced intermediate results. While rice yields were higher in these rotations than when rainfed rice was grown alone, weed biomass remained high due to minimal competition with weeds during the crop rotation cycle especially with groundnut. For RSC, nematode control was limited as both sorghum and cowpea are host plants for nematodes. Despite a year with no crop income with the RVC rotation, profitability was higher mainly due to the increased rice yield and reduced field management costs. The choice of species is thus crucial to optimise ecosystem functions adapted to farmers’ context and objectives.

A major part of tomato varieties that grow in greenhouses are so-called indeterminate growth and meaning that they can grow indefinitely. Despite this characteristic, a slowdown of the plant's metabolism and a decrease of vigour can be observed after several months of cultivation. This weakening is mainly due to excessive stem length as well as potential stem or crown injuries. In this study, the ability of the tomato plant to form and develop adventitious roots at the stem is used to root the plant anew and thus reduce the stem length.; La majorité des variétés de tomates cultivées sous serre sont dites à croissance indéterminée, ce qui signifie qu'elles peuvent croitre de façon illimitée. Malgré cette caractéristique, on observe un ralentissement du métabolisme de la plante et une diminution de la vigueur au bout de plusieurs mois de culture. Cet affaiblissement est principalement dû à une longueur excessive de tige ainsi qu’à de potentielles blessures sur la tige ou au niveau du collet. Dans cette étude, la faculté de la tomate à former et développer des racines adventives au niveau de la tige est utilisée pour ré-enraciner la plante et ainsi diminuer la longueur de tige.

Calls for ecological principles in agriculture have gained momentum. Intercropping systems have long been designed by growing two, or more, annual crop species in the same field, aiming for a better resource use efficiency. However, assembly rules for their design are lacking. Notably, it is still unknown whether species performances are maximized during both the vegetative and reproductive phases given the sensitivity of reproductive allocation rules to resource limitation. Interestingly, ecological theory provides expectations regarding putative invariance of plant reproductive allometry (PRA) under non-limiting conditions for plant growth. Here we examined whether and how PRA changes in response to plant-plant interactions in intercropping systems, which can inform both ecological theory and the understanding of the functioning of intercropping systems.We analyzed a dataset of 28 field cereal-legume intercropping trials from various climatic and management conditions across Western Europe. PRA was quantified in both mixing and single-species situations.PRA was positively impacted in specific management conditions, leading to a greater increase in yield for a given increase in plant size. Variations in PRA were more beneficial for legumes grown in unfertilized mixture, which explains their use as a key component in actual intercrop systems. The response for cereals was similar but less pronounced in magnitude, and was greater under limiting resource conditions. Focusing on intercropping conditions, hierarchical competition (indicated by biomass difference between intercropped species) appears as a strong driver of the reproductive output of a given species.Synthesis and applications. Plant reproductive allometry behaves in crop species in the same way as it does in wild species. However, contrary to theoretical expectations about an overall invariance of PRA, we highlighted taxon-specific and context-dependent effects of plant-plant interactions on PRA. This systematic deviation to PRA expectations could be leveraged to cultivate each species up to its reproductive optimum while accounting for the performance of the other, whether farmer’s objective is to favor one species or to reach an equilibrium in seed production. Sowing density and cultivar choice could regulate the biomass of each component, with specific targets derived from allometric relationships, aiming for an optimal reproductive allocation in mixtures.

International audience; Conservation agriculture (CA) is one strategy with which both sustainability and productivity can be achieved by improving soil health. However, linkages between practices, soil health and cropping system performance remain poorly disentangled. We assessed the relationships between soil health and cropping system performance for three maize-based cropping systems in New Caledonia. Two CA systems, one with direct seeding into a mixed species dead mulch (CA-DM) and one into a stylo living mulch (CA-LM), were compared to a conventional tillage (CT) system. CA vs. CT experiment started in 2011, whereas the differentiation between CA-DM and CA-LM was initiated in 2017 only. In 2018, soil health was evaluated using Biofunctool (R), a set of ten in-field tools that assess soil carbon transformation, structure maintenance and nutrient cycling functions. The performance of the three cropping systems were assessed by monitoring weeds, maize growth and yield components. Structural equation modelling (SEM) was used to disentangle the links between agricultural management, soil health and cropping system performance. Soil structure maintenance and nutrient cycling functions were higher under CA-DM and CA-LM than under CT, and carbon transformation function was higher under CA-DM than under CT and CA-LM. Overall, the soil health index (SHI) was 1.3-fold higher under CA systems than under CT. Cropping system management had both direct and indirect effects on soil functioning and crop productivity leading to a 1.3-fold higher yield under CA than under CT. The direct and indirect effects of CA systems on soil health had positive impacts on ecosystem services (i.e., productivity, weed regulation and soil ecosystem services). Such integrative approaches that account for the relationships and possible trade-offs between cropping system components enable a better understanding of the effects and the performance of practices, and support adaptive agricultural management.

International audience; Identifying locally adapted and adopted efficient practices can be a step towards the agroecological transition of irrigated plains of the Southern Mediterranean region. However, these types of practices - often little known - are drowned within a wide range of practices. The objective of this study was, first, to elaborate a method to describe this diversity in a semi-arid irrigated landscape, at both the plot and farm scales; second, to show the main characteristics of these types of crop management; and third, to question their sustainability according to agroecological principles. To do so, this paper focused on Southern Mediterranean irrigated cropping systems as i) studies on management routes are scarce with regard to this region; ii) irrigated landscapes are known for their high level of natural, technical and financial constraints, often favoring more intensive farming practices regarding chemical inputs. A series of semi-directive interviews were conducted in order to assess farmers’ management of chili-pepper-based (Capsicum annuum) cropping systems, a widespread crop in the Merguellil plain, Central Tunisia. The "Typ-iti” method, combining multivariate analysis, clustering and association rules, was used to characterize the diversity of technical management routes (TMR) of these systems. The environmental sustainability was qualitatively accessed by classifying the clusters of TMRs obtained according to their potential impact on natural resources. Then, these management routes were qualitatively associated to some farm structural characteristics, to analyze their diversity at the farm level. These enabled to distinguish a gradient of farming practices and characteristics, respectively at both plot and farm scales relative to environmental impacts. The study showed that some agroecology-compatible TMRs coexisted with conventional TMRs for chili-pepper-based cropping systems. Our method characterized three main groups: i) a group of intensive TMRs regarding chemical input powered especially by tenant farmers, ii) an intermediary group iii) a moderate group powered by land owners. Throughout these main groups, seven types of TMRs were described. These were always comprised of both agroecology and non-agroecology-compatible technical operations. This coexistence of diversely impacting practices challenges agroecology in multiple ways. Fertilization management appeared as a major issue in the study zone, often resulting in high applied doses. These findings could allow actors in charge of agriculture to better focus their action. However, the study did not take into account the outputs of the studied systems, so that their productivity and environmental impacts have not yet been assessed in a quantitative manner. For future studies, the paragons obtained from our analysis are typical cases that could be studied for such a purpose.

International audience; Intensive maize cultivation in the uplands of North-west Vietnam has resulted in soil erosion leading to reduced maize yields along with negative impacts downstream. Despite the introduction of sustainable agricultural technologies over many years, adoption rates are low mostly due to their incompatibility with existing farming systems and lack of secure markets for alternative crops. In addition, the temporary nature of development programmes and limited capacity of government extension systems have resulted in limited spread of technology, and where they have been introduced, unable to secure long-lasting commitments from farmers. In this study, we explore an alternative model involving maize value chain actors for attaining more durable transition towards sustainable maize farming systems. We find maize traders operating at lower levels of the value chain with active engagement with the farming community to be best suited for engaging in technology dissemination. While their involvement may require additional incentives and oversight from the government it is imperative that support for commercialization through promising market links are established to achieve a more meaningful shift towards sustainable farming methods.

International audience; In the cotton-production zone of Burkina Faso, poor soil fertility and limited access to appropriate fertilizers call for alternative approaches to sustain productivity, such as the introduction of more legumes into the agroecosystem. Legumes have nearly disappeared from local cropping systems under the pressure of the cotton monocropping model. To develop new legume-based cropping systems using a bottom-up approach, this study was based on local farmers' agroecological innovations. In a first step, called on-farm innovation tracking, five innovative legume-based cropping systems were identified and characterized on farms located in the study area through interviews with "innovative farmers" who had designed and implemented these cropping systems: (i) Sorghum and legume (cowpea, soybean or peanut) intercropping in rotation with maize or cotton; (ii) Soybean as a cash crop in rotation with maize or cotton; (iii) Red cowpea intra-annual succession with a biomass crop; (iv) Mucuna in rotation with maize; and (v) Pigeon pea in rotation with maize. In a second step, these five "innovative cropping systems" (ICSs) were implemented in "participatory prototyping trials" (PPTs) in two communities located in the study area were they were evaluated during field days by local farmers ("field-day farmers") having no previous experience with ICSs. By comparing evaluations made by innovative farmers with those of field-day farmers, it was shown that (i) locally implemented ICSs adapted to local drivers of change are of great interest to other farmers, and (ii) the study's two-step participatory approach is an original and relevant way to co-design and introduce innovations.

• Crop diversification is a dynamic pathway towards sustainable agrifood systems. • Technological and institutional barriers restrict uptake of crop diversification. • More coordination and cooperation among agrifood system stakeholders is required. • The European Crop Diversification Cluster calls for multiactor networks. European cropping systems are often characterized by short rotations or even monocropping, leading to environmental issues such as soil degradation, water eutrophication, and air pollution including greenhouse gas emissions, that contribute to climate change and biodiversity loss. The use of diversification practices (i.e., intercropping, multiple cropping including cover cropping and rotation extension), may help enhance agrobiodiversity and deliver ecosystem services while developing new value chains. Despite its benefits, crop diversification is hindered by various technical, organizational, and institutional barriers along value chains (input industries, farms, trading and processing industries, retailers, and consumers) and within sociotechnical systems (policy, research, education, regulation and advisory). Six EU-funded research projects have joined forces to boost crop diversification by creating the European Crop Diversification Cluster (CDC). This Cluster aggregates research, innovation, commercial and citizen-focused partnerships to identify and remove barriers across the agrifood system and thus enables the uptake of diversification measures by all European value-chain stakeholders. The CDC will produce a typology of barriers, develop tools to accompany actors in their transition, harmonize the use of multicriteria assessment indicators, prepare policy recommendations and pave the way for a long-term network on crop diversification.

DéciFlorSys est un outil stratégique (numérique) qui accompagne son utilisateur à concevoir ou améliorer un système de culture vers des pratiques plus agroécologiques. Conçu avec un point de vue particulier focalisé sur les impacts des adventices, à partir de processus complexes, son utilisation nécessite une formation adaptée. L’outil a été conçu dans une démarche de co-construction avec ses futurs utilisateurs (conseillers et agriculteurs). La formation-action a été construite sur la même démarche.Ce mémoire problématise le processus de co-construction de la formation. Concrètement,un panorama des formations à la reconnaissance et la gestion des adventices et à la prise en main d’outils d’aide à la décision a été effectué. Complété par des entretiens avec des formateurs et de potentiels utilisateurs, ce mémoire s’est notamment intéressé aux représentations qu’ils avaient des adventices et de leur gestion pour construire la formation. Il pose la question suivante : en quoi une diversité de conseillers agricoles peut-elle contribuer à la co-construction d’une formation-action à un outil d’aide à la gestion agroécologique pluriannuelle de la flore adventice ?En termes de résultats, la mise en œuvre de la co-construction a permis de développer la formation-action basée sur les échanges entre pairs, aidant les utilisateurs à se projeter dans l’usage de DéciFlorSys. Ces potentiels participants, bien qu’ayant des visions nuancées de la gestion des adventices, ont su partager le même atelier de formation à l’outi

International audience; Modern agriculture needs to develop transition pathways toward agroecological, resilient and sustainable farming systems. One key pathway for such agroecological intensification is the diversification of cropping systems using intercropping and notably cereal-grain legume mixtures. Such mixtures or intercrops have the potential to increase and stabilize yields and improve cereal grain protein concentration in comparison to sole crops. Species mixtures are complex and the 4C approach is both a pedagogical and scientific way to represent the combination of four joint effects of Competition, Complementarity, Cooperation, and Compensation as processes or effects occurring simultaneously and dynamically between species over the whole cropping cycle. Competition is when plants have fairly similar requirements for abiotic resources in space and time, the result of all processes that occur when one species has a greater ability to use limiting resources (e.g., nutrients, water, space, light) than others. Complementarity is when plants grown together have different requirements for abiotic resources in space, time or form. Cooperation is when the modification of the environment by one species is beneficial to the other(s). Compensation is when the failure of one species is compensated by the other(s) because they differ in their sensitivity to abiotic stress. The 4C approach allows to assess the performance of arable intercropping versus classical sole cropping through understanding the use of abiotic resources.

The EIP-Agri multiactor approach was exemplified during a 3-day workshop with 63 project participants from the EU H2020 funded project "Redesigning European cropping systems based on species MIXtures". The objective was to share firsthand experience of participatory research among researchers who were mostly not familiar with this approach. Workshop participants were divided into smaller multidisciplinary groups and given the opportunity to interact with representatives from eight actor positions in the value chain of the agrifood cooperative Terrena located in Western France. The four stages of the workshop were: (1) key actor interviews, (2) sharing proposed solutions for overcoming barriers, and (3) developing possible interdisciplinary concepts. Expressions of frustration were recorded serving both as a motivation for group members to become more aware of the scientific concerns and practices of their colleagues, as well as a recognition that some researchers have better skills integrating qualitative approaches than others. Nevertheless, the workshop format was an effective way to gain a common understanding of the pertinent issues that need to be addressed to meet overall multiactor-approach objectives. Working with the actor networks was identified and emphasized as a means to overcome existing barriers between academia and practice in order to coproduce a shared vision of the benefits of species mixture benefits. (C) The Author(s) 2021. Published by Higher Education Press.

In many regions of the world characterized by strong seasonal and interannual hydroclimatic variability, water reservoirs are considered as a solution to secure the water resource for its use in crop irrigation. However, the development and multiplication of reservoirs in an agricultural watershed can have significant cumulative effects, both on hydrology and other environmental components (geomorphology, ecology, etc.). Modeling is an approach to estimate and quantify these cumulative effects. The objective of this thesis was to develop and test a distributed agro-hydrological model that couples hydrology, crop development and farmers' decisions in a watershed with water reservoirs. This model, called MHYDAS-Small-Reservoirs, has the originality of explicitly representing the main elements of the watershed (plot, reach, reservoir, water table) and the hydrological and agronomic links between these elements. The model has been numerically and computationally verified. It has been applied and evaluated on a case study, the Gélon watershed, in France (20 km²).The model simulates satisfactorily the flows and the crop yields. In addition, the databases used to parameterize the model are mostly national, which would allow an application of the model to other watersheds.We analyzed the interest of the model to quantify and understand the cumulative effects of reservoirs on watershed hydrology and crop yields in a variety of configurations in terms of climate, reservoir density, and crop rotation. This analysis was carried out on the basis of theoretical situations in the Gélon watershed. The simulations show in particular the interest of the model to evaluate both local and cumulative effects, and the links between these effects. In addition, they allow us to identify a certain number of counter-intuitive results, to quantify them and to understand them. Finally, these simulations have demonstrated and explained local effects associated with reservoirs that were contrary to the effect of all reservoirs in the watershed., Dans beaucoup de régions du monde marquées par une forte variabilité saisonnière et interannuelle hydroclimatique, les retenues d'eau sont considérées comme une solution pour sécuriser la ressource en eau en vue de son utilisation pour l'irrigation des cultures. Le développement et la multiplication des retenues dans un bassin versant agricole peuvent cependant avoir des effets cumulés importants, aussi bien sur l'hydrologie que d'autres composantes environnementales (géomorphologie, écologie…). La modélisation constitue une approche pour estimer et quantifier ces effets cumulés. Cette thèse avait pour objectif de développer et tester un modèle agro-hydrologique distribué qui couple hydrologie, développement des cultures et décisions des agriculteurs dans un bassin versant avec retenues d'eau. Ce modèle, appelé MHYDAS-Small-Reservoirs, a pour originalité de représenter explicitement les principaux éléments du bassin versant (parcelle, bief, retenue, nappe) et les liens hydrologiques et agronomiques entre ces éléments. Le modèle a été vérifié numériquement et informatiquement et a été appliqué et évalué sur un cas d'étude, le bassin versant du Gélon, France (20 km²). Le modèle simule de manière satisfaisante débits et rendements des cultures. En outre, les bases de données utilisées pour paramétrer le modèle sont pour la plupart nationales, ce qui permettrait d'appliquer le modèle à d'autres bassins versants.Nous avons analysé l'intérêt du modèle pour quantifier et comprendre les effets cumulés des retenues sur le fonctionnement hydrologique du bassin versant et sur les rendements des cultures dans une diversité de configurations en termes de climat, de densité de retenues et d'assolement. Cette analyse a été effectuée à partir de situations théoriques du bassin versant du Gélon. Les simulations montrent en particulier l'intérêt du modèle pour évaluer à la fois les effets locaux et les effets cumulés, et les liens entre ces effets. De plus, elles permettent d'identifier un certain nombre de résultats contre-intuitifs, de les quantifier et de les comprendre. Enfin, ces simulations ont permis de démontrer et d'expliquer des effets locaux associés aux retenues contraires à l'effet de l'ensemble des retenues sur le bassin versant.

There is an urgent need to investigate how to manage weeds with fewer or no herbicides in arable farming.The questions of weed harmfulness, herbicide efficacy, the effects of herbicide use on crop yields, andthe effect on crop production of reducing herbicides have been addressed over the years but results oftenappear contradictory. Here, we critically reviewed published studies focusing on the interactions betweenherbicide use, weeds and crop yield. We demonstrate that many inconsistencies result from differencesin methodologies and in the conceptual model that links the three items. Our main findings are: (1) Themethods used to assess weed impact on crop production are often inadequate, yet, there is evidencethat, if not compensated by proper combined sets of cultural techniques, herbicide reduction increasesweed infestation ; (2) Reducing herbicide use rarely increases crop yield loss if farmers compensate byother cultural practices ; (3) Comprehensive cropping-system studies are needed that explicitly includeweeds and disentangle herbicide impacts from the effect of other practices on weeds and on cropproduction. We conclude that herbicide use can be reduced without losing crop production if croppingsystems are redesigned by combining agronomic and biodiversity-based levers and accounting for theproduction context.; Résumé : Pour comprendre comment gérer les adventices avec peu ou pas d'herbicides en grandes cultures, étudier la nuisibilité des adventices, l'efficacité et les effets des herbicides et de leur réduction sur le rendement est nécessaire. Cette question a été étudiée depuis des années mais les résultats apparaissent souvent contradictoires. Notre article propose une analyse critique des publications scientifiques traitant des relations entre usage d'herbicides, adventices et rendement. Nous démontrons que de nombreuses incohérences résultent de différences méthodologiques et du choix liant ces trois items. Les méthodes utilisées pour analyser la relation adventices-production sont souvent inadéquates ; cependant, il y a des preuves que, sans compensation par des combinaisons adaptées de techniques culturales, la réduction de l’utilisation des herbicides augmente les densités adventices. Des études à l’échelle du système de culture sont indispensables, qui explicitement incluent les adventices et démêlent les effets des herbicides de ceux d'autres pratiques, tant sur les adventices que sur la production. Nous concluons que l'usage d'herbicides peut être réduit sans perte de production si les systèmes de culture sont reconçus en combinant des leviers agronomiques, tenant compte du contexte de production.Abstract : Relationships between herbicide use intensity, weeds and yield: critical analysis of current methods and resultsThere is an urgent need to investigate how to manage weeds with fewer or no herbicides in arable farming. The questions of weed harmfulness, herbicide efficacy, the effects of herbicide use on crop yields, and the effect on crop production of reducing herbicides have been addressed over the years but results often appear contradictory. Here, we critically reviewed published studies focusing on the interactions between herbicide use, weeds and crop yield. We demonstrate that many inconsistencies result from differences in methodologies and in the conceptual model that links the three items. Our main findings are: (1) The methods used to assess weed impact on crop production are often inadequate, yet, there is evidence that, if not compensated by proper combined sets of cultural techniques, herbicide reduction increases weed infestation ; (2) Reducing herbicide use rarely increases crop yield loss if farmers compensate by other cultural practices ; (3) Comprehensive cropping-system studies are needed that explicitly include weeds and disentangle herbicide impacts from the effect of other practices on weeds and on crop production. We conclude that herbicide use can be reduced without losing crop production if cropping systems are redesigned by combining agronomic and biodiversity-based levers and accounting for the production context.

Ce volume regroupe les textes issus du programme ANR-15-CE18-0007 « CoSAC - Conception de Stratégies durables de gestion des Adventices dans un contexte de Changement (Climat, pratiques agricoles, biodiversité) »; The CoSAC project aimed to propose new agricultural systems that reconciled reduced herbicide use with preservation of crop production, farmers' income and biodiversity in arable crops. In this project participatory workshops were organized with farmers to design such innovative cropping systems. A symposium was held for scientists, students, crop advisors and farmers at the end of the project in 2019. There, one of the farmers participating in the workshops of the DEPHY farm group from the Eure department testified to his experience in this approach. His testimony focused on the place of croppingsystem design in the "cropping system" approach, the contribution of research studies to this approach, his participation in the design process, the fine tuning of a tool aiming to support cropping-system design.; Le projet CoSAC visait à proposer des nouveaux systèmes agricoles qui concilient réduction d'usage des herbicides, maintien de la production et du revenu agricole et conservation de la biodiversité en grandes cultures. Un des volets du projet était constitué par des ateliers de co-conception de systèmes de culture avec des agriculteurs. Lors du colloque final du projet en 2019, un des agriculteurs du groupe DEPHY Ferme de l'Eure participant à ces ateliers témoignait de son expérience dans ce travail. Son témoignage concernait plus particulièrement la place de la conception dans l'approche "système de culture", l''enrichissement de cette démarche par des travaux de recherche, sa participation à un processus de conception, d'ajustement et de mise au point d'un outil d'aide à la conception de systèmes de culture.

Prod 2019-15kEASPEGESTADINRAAGROSUPDOCT; Three methods of innovative design for cropping systems were compared for their contribution tosustainable weed management: (i) de novo expert design by multiple stakeholders; co-design by farmers(ii) of one cropping system during workshops; (iii) of cropping systems for each farmer member of aDEPHY network group over several years. The weed simulation model FLORSYS was used to evaluatethese systems with six indicators, describing weed harmfulness for crop production, weed contribution tobiodiversity and herbicide use. A principal component analysis on this dataset illustrated that there is nocorrelation between herbicide use and weed harmfulness for crop production. De novo expert design ledto bigger changes in practices and systems performances, compared to co-design with farmers, especially when innovative systems are designed for each farmer of a group. The evolution of sustainability of thesecropping systems was assessed with the multicriteria assessment model DEXiPM and again morechanges, often positive, were found with the design methods (i) and (ii). However, only a few innovativecropping systems designed with method (iii) were able to reduce weed harmfulness for production whileenhancing sustainability, thanks to major changes planned in crop sequences (winter wheat reductionand sugarbeet removal), after ten years of step-by-step design. These results illustrate differences andcomplementarities of these design methods.; Trois démarches de conception de systèmes de culture ont été comparées sur leur contribution à la gestion durable des adventices : (i) conception par expertise d’acteurs multiples ; co-conception par des agriculteurs (ii) d’un système innovant lors d’ateliers ponctuel ou (iii) de systèmes innovants pour chaque agriculteur d’un groupe sur une démarche de long terme. Les systèmes définis ont été simulés avec le modèle de dynamique de la flore adventice FLORSYS. Une Analyse en Composantes Principales des résultats de six indicateurs décrivant la nuisibilité des adventices pour la production, la diversité des adventices et l’intensité d’usage d’herbicides a été réalisée. Tout d’abord, la nuisibilité des adventices et l’usage d’herbicides ne sont pas corrélés. Ensuite, les systèmes innovants conçus selon la méthode (i) conduisent à des changements plus importants et contrastés, à l’inverse de la co-conception par des agriculteurs, particulièrement avec des systèmes conçus pour chaque agriculteur. Enfin, l’évolution de la durabilité a été évaluée avec le modèle d’évaluation multicritère DEXiPM. La durabilité évolue plus fréquemment, de manière positive pour les méthodes de conception (i) et (ii). Néanmoins, les seuls systèmes innovants combinant réduction significative de la nuisibilité des adventices pour la production et augmentation de la durabilité sont issus du groupe (iii), avec des modifications profondes de la rotation (réduction du blé tendre, abandon de la betterave) envisagées après 10 ans de conception pas-à-pas. Ces résultats illustrent les différences et complémentarités de ces différentes méthodes.Abstract : Comparing methods for designing innovative cropping systems aiming at sustainable weed managementThree methods of innovative design for cropping systems were compared for their contribution to sustainable weed management: (i) de novo expert design by multiple stakeholders; co-design by farmers (ii) of one cropping system during workshops; (iii) of cropping systems for each farmer member of a DEPHY network group over several years. The weed simulation model FLORSYS was used to evaluate these systems with six indicators, describing weed harmfulness for crop production, weed contribution to biodiversity and herbicide use. A principal component analysis on this dataset illustrated that there is no correlation between herbicide use and weed harmfulness for crop production. De novo expert design led to bigger changes in practices and systems performances, compared to co-design with farmers, especiallyCavan N., et al.190 Innovations Agronomiques 81 (2020), 189-200when innovative systems are designed for each farmer of a group. The evolution of sustainability of these cropping systems was assessed with the multicriteria assessment model DEXiPM and again more changes, often positive, were found with the design methods (i) and (ii). However, only a few innovative cropping systems designed with method (iii) were able to reduce weed harmfulness for production while enhancing sustainability, thanks to major changes planned in crop sequences (winter wheat reduction and sugarbeet removal), after ten years of step-by-step design. These results illustrate differences and complementarities of these design methods.

To evaluate the resilience of innovative weed management strategies, the impact of climate change wasinvestigated with a regionalized simulation approach. First, we checked that the protocol for dynamicregionalisation correctly mimicked the climate observed over 1980-2016. Then, the protocol was appliedto two periods (2010-2040 and 2069-2099). Finally, we compared existing and prospective croppingsystems in terms of weed management and impacts on crop production and biodiversity, with these twoclimate trajectories. To do so, 44 cropping systems from 5 regions were simulated with the weed dynamicsmodel FlorSys. Our results show that surface temperature will increase in average by approx. 4°C at theend of the century with the RCP8.5 trajectory. Three cropping system types were identified in responseto these climate changes, those whose weed harmfulness for crop production (1) decreased,(2) increased, particularly with trajectory RCP8.5 from 2069-2099, (3) was average but whose weedcontribution to biodiversity increased. The study allowed identifying the management levers essential forinnovative cropping systems that are robust relatively to climate change.; Pour tester la robustesse des stratégies innovantes de gestion des adventices, le changement climatique a été abordé par une approche de simulations climatiques régionalisées. D'abord, nous avons vérifié que le protocole de régionalisation dynamique mimait correctement le climat observé sur la période 1980-2016. Ensuite, ce protocole a été appliqué à deux trajectoires de forçage radiatif (RCP4.5 et RCP8.5) définies pour l'exercice d'intercomparaison des modèles climatiques globaux (CMIP5) afin d'évaluer l'incertitude associée aux émissions de gaz à effet de serre attendue sur la deuxième moitié du 21 e siècle. Enfin, nous avons comparé des systèmes de culture existants et prospectifs, en terme de gestion de la flore adventice et de son impact sur la production agricole et la biodiversité, avec ces trajectoires climatiques. Pour cela, 44 systèmes de 5 régions ont été simulés avec le modèle de dynamique de la flore adventice FLORSYS. Nos résultats montrent que les températures de surface augmentent en moyenne de ~4 °C en fin de siècle pour la trajectoire RCP8.5. Face à ces changements climatiques, trois types de systèmes de culture ont été identifiés : ceux dont la nuisibilité des adventices pour la production (1) diminue ; (2) augmente, particulièrement avec la trajectoire RCP8.5 sur la période 2069-2099 ; (3) est moyenne mais dont la contribution des adventices à la biodiversité augmente. Ces travaux identifient les leviers à prioriser pour définir des systèmes de culture innovants et robustes face au changement climatique.

International audience; To evaluate the resilience of innovative weed management strategies, the impact of climate change wasinvestigated with a regionalized simulation approach. First, we checked that the protocol for dynamicregionalisation correctly mimicked the climate observed over 1980-2016. Then, the protocol was appliedto two periods (2010-2040 and 2069-2099). Finally, we compared existing and prospective croppingsystems in terms of weed management and impacts on crop production and biodiversity, with these twoclimate trajectories. To do so, 44 cropping systems from 5 regions were simulated with the weed dynamicsmodel FlorSys. Our results show that surface temperature will increase in average by approx. 4°C at theend of the century with the RCP8.5 trajectory. Three cropping system types were identified in responseto these climate changes, those whose weed harmfulness for crop production (1) decreased,(2) increased, particularly with trajectory RCP8.5 from 2069-2099, (3) was average but whose weedcontribution to biodiversity increased. The study allowed identifying the management levers essential forinnovative cropping systems that are robust relatively to climate change.; Pour tester la robustesse des stratégies innovantes de gestion des adventices, le changement climatique a été abordé par une approche de simulations climatiques régionalisées. D'abord, nous avons vérifié que le protocole de régionalisation dynamique mimait correctement le climat observé sur la période 1980-2016. Ensuite, ce protocole a été appliqué à deux trajectoires de forçage radiatif (RCP4.5 et RCP8.5) définies pour l'exercice d'intercomparaison des modèles climatiques globaux (CMIP5) afin d'évaluer l'incertitude associée aux émissions de gaz à effet de serre attendue sur la deuxième moitié du 21 e siècle. Enfin, nous avons comparé des systèmes de culture existants et prospectifs, en terme de gestion de la flore adventice et de son impact sur la production agricole et la biodiversité, avec ces trajectoires climatiques. Pour cela, 44 systèmes de 5 régions ont été simulés avec le modèle de dynamique de la flore adventice FLORSYS. Nos résultats montrent que les températures de surface augmentent en moyenne de ~4 °C en fin de siècle pour la trajectoire RCP8.5. Face à ces changements climatiques, trois types de systèmes de culture ont été identifiés : ceux dont la nuisibilité des adventices pour la production (1) diminue ; (2) augmente, particulièrement avec la trajectoire RCP8.5 sur la période 2069-2099 ; (3) est moyenne mais dont la contribution des adventices à la biodiversité augmente. Ces travaux identifient les leviers à prioriser pour définir des systèmes de culture innovants et robustes face au changement climatique.

In the Northern mountainous region of Vietnam, cassava–cowpea intercropping system has been widely promoted with support from the local agricultural department. However, cowpea yield is often limited because of a low Biological Nitrogen Fixation (BNF) activity due to its low natural nodulation and lack of available effective Rhizobium products. The aim of this study was to identify the most effective native rhizobia isolate nodulating cowpea with the potential to increase BNF and yield of cowpea. A greenhouse experiment was initially conducted with five treatments: three native rhizobia isolates (CMBP037, CMBP054, and CMBP065); a control (no inoculation and no N application); and N+ (no inoculation, application of N as KNO3). Field inoculations were carried out and the treatments were as follows: a control (no inoculation); CMBP (037+054) – a mixture of strains from Mau Dong; CMBP065 strain from Cat Thinh. CMBP054 and CMBP065 had the highest nodulation in the greenhouse (46.4 and 60.7 nodules plant−1, respectively) and were rated as effective with symbiotic efficiency (SEF) of 54.56 and 55.73%, respectively. In the field, CMBP (037+054) recorded significantly higher nodulation (19.4 nodules plant−1) than the control (11.7 nodules plant−1). CMBP (037+054) also increased cowpea shoot dry weight, shoot N, and yield by 28.6, 4.9, and 10.5%, respectively, compared to the uninoculated control. This effect was slope dependent (statistically significant in moderate and steep slope, not with gentle slope). Besides, the high expansion rate of intercropping with cowpea showed the high adoption level of these agroecological practices by local farmers. This study reveals the potential of native rhizobia inoculation to enhance soil fertility and sustainable agriculture in the Northern mountainous region of Vietnam and proposes enhanced efforts to promote the availability and utilization of effective inoculants for cowpea.

Weeds and D. stramonium management is a major challenge for farmers and human food chain as popcorn. Before redesigning cropping systems (CS) for an ecological intensive weed management, CS need to be characterized and their weeds management efficiency assessed. This is the aim of this study conducted in a network of 16 popcorn farmers in the South-West of France. From farmers surveys, CS were mainly characterized by the diversity of the crop rotation and the weed management. Two soil types were identified influencing the type of CS. Abundance, composition and diversity of weed communities were measured in one field of each farmer after weeding. A strong distinction between fields managed in organic agriculture and in conservation agriculture was observed. In these fields, weed communities had a greater abundance than in those managed in conventional agriculture. Weed biomass was about 192 ± 188, 40 ± 22 et 1 ± 3 g MS.m-2 respectively in these different types of management. The orientation of CS provided a better explanation of the differences seen in the characteristic of weed communities than our typology due to a very low weed abundance in conventional. Fields managed in organic agriculture were more vulnerable to D. stramonium infestation as in those where the seed spacing was 80 cm. In these fields, D. stramonium was more abundant. Based both on the literature and our results, a redesign framework of CS was proposed to modify the CS in function of the presence or not of D. stramonium in the field.; La gestion des adventices et de D. stramonium est un enjeu majeur des agriculteurs et des filières dédiées à l’alimentation humaine comme le popcorn. Avant de repenser les systèmes de culture (SDC) pour une gestion écologiquement intensive des adventices, ils doivent être caractérisés et leur efficacité de gestion des adventices évaluée, objets de notre étude menée dans un réseau de 16 agriculteurs produisant du maïs popcorn dans le Sud-Ouest de la France. À partir d’enquêtes réalisées auprès des agriculteurs, les SDC ont été caractérisés selon la diversité de la rotation et la gestion des adventices. Deux types de sol ont été identifiés impactant le SDC mis en place. Les mesures des caractéristiques des communautés adventices présentes dans les parcelles suivies après désherbage, montre notamment une plus forte abondance des communautés adventices entre les parcelles en agriculture biologique (AB) et en agriculture de conservation, que celle en agriculture « conventionnelle ». Les biomasses étaient respectivement de 192 ± 188, 40 ± 22 et 1 ± 3 g MS.m-2 à floraison du maïs. L’orientation des SDC explique mieux les différences observées sur les communautés adventices que notre typologie due à une très faible abondance des adventices en « conventionnelle ». Les parcelles en AB et celles où l’écartement de semis est de 80 cm sont plus à risque pour D. stramonium étant plus abondant sur ces parcelles. À partir de la littérature et de nos résultats, un cadre de reconception des SDC est proposé orientant cette étape selon la présence ou non de D. stramonium dans la parcelle.

Les sols d'altitude du sud de la Basse-Terre (andosols) sont caractérisés par des stocks de matière organique très élevés qui peuvent être particulièrement sensibles à l'intensification du travail du sol et au réchauffement climatique. Cette sensibilité est déterminée par la vitesse de décomposition de la matière organique. Dans cette étude nous avons estimé pour la première fois le gradient altitudinal du taux de décomposition in-situ de la matière organique du sol, et observé qu'il diminue dans les sols de haute altitude, ce qui explique leurs plus grands stocks en matière organique.Le rendement de la banane, la quantité de résidus de récolte et le carbone apporté au sol par ces résidus diminuent avec l'altitude, mais ils ne déterminent pas le gradient de matière organique. D'ailleurs, les gradients altitudinaux de température et de pluviométrie, ainsi que la disponibilité de nutriments, ne peuvent pas expliquer la forte réduction du taux de décomposition en altitude. Ce dernier est surtout contrôlé par la minéralogie des sols, laquelle détermine l'accroissement en altitude de la protection physique de la matière organique vis-à-vis de la dégradation provoquée par l'activité microbienne du sol.Ce phénomène a d'importantes conséquences sur la résilience des sols aux impacts agro-environnementaux, laquelle augmente fortement dans les sols de haute altitude. Les résultats obtenus apportent des pistes intéressantes aussi bien pour la recherche agronomique que pour la gestion de pratiques culturales dans le gradient altitudinal du sud de la Basse-Terre.

International audience; The evolution of cocoa farming was quickly confronted with the development of pests and diseases. These sanitary constraints have shaped the geographical distribution of production over the centuries. Current climate change adds an additional constraint to the plant health constraints, making the future of cocoa farming more uncertain. Climate change is not only affecting the areas where cocoa is grown for physiological reasons, particularly in relation to changes in water regimes, but also affects the distribution of pests and diseases affecting this crop. These different points are discussed in the light of the trajectories observed in the different cocoa-growing areas. The breeding programs of cocoa trees for sustainable resistance to plant health constraints and climate change are therefore particularly important challenges for cocoa farming, with the other management practices of plantations.

National audience; The data presented in this article describe 21 species that can be found in banana cropping systems: 17 cover crops species, 2 spontaneous species and 2 cultivars of banana. The cover crop species belongs mainly to Fabaceae family, but also to Poaceae, Euphorbiacea and Asteraceae. Four repetition of each species were cultivated individually, in the field, under non-limiting conditions. 40 variables were measured on whole plant, leaves and roots, at flowering or after six months of growth for longer cycle species. This dataset is made available to provide data on these species, enable comparisons between datasets and meta-analysis on cover crop or on species presented in arable fields. The data presented in this article were used in the research articles entitled “Trait-based characterisation of cover plants' light competition strategies for weed control in banana cropping systems in the French West Indies” (Tardy et al. 2015) and “Trait-based characterization of soil exploitation strategies of banana, weeds and cover plant species” (Tardy et al. 2017).

Master; Mon stage a été effectué à l’INRAE de Colmar au sein de l’équipe AGISEM (Agriculture, Biodiversité, Services écosystémiques et évaluation Multicritères) de l’UMR LAE (Laboratoire Agronomie et Environnement). Il a pour objectifs la caractérisation de la flore du vignoble et sa mise en relation avec les pollinisateurs qui y sont observés. L’érosion de la biodiversité au sein des paysages agricoles en générale et dans le vignoble en particulier est une réalité inquiétante en raison d’une agriculture devenue intensive et nécessitant une utilisation importante de produits phytopharmaceutiques. Il est donc important de favoriser la biodiversité dans les paysages agricoles car elle permet d’équilibrer les écosystèmes et de rendre de nombreux services écosystémiques aux cultures. Cette étude a été réalisée sur un « essai Système » en viticulture à Wintzenheim dans le cadre du projet SALSA (Systèmes viticoles agroécologiques mobilisant la résistance variétale et les régulations naturelles). L’étude a pour but de voir l’importance de la caractérisation de la flore en milieu viticole pour la prédiction de la pollinisation, l’importance de l’implantation de couverts végétaux sur les interrangs et l’impact de l’itinéraire technique sur l’installation d’une flore diversifiée. Pour ce faire, nous avons en premier lieu comparé la biodiversité floristique au sein des différentes méthodes de productions et les types d’agricultures mis en place sur l’essai Système. Ensuite nous avons comparé la biodiversité floristique au sein des interrangs enherbés avec celle des interrangs travaillés et cavaillons. Les résultats obtenus démontrent qu’un système de culture dont l’itinéraire technique induit une faible pression sur la végétation, ainsi que la mise en place de couverts végétaux présentent un intérêt en termes d’attraction des pollinisateurs. Les résultats indiquent également que l’itinéraire technique joue un rôle important sur la richesse spécifique, les espèces rencontrées et leur répartition.

International audience; Sustainable intensification (SI) of farming systems aims to increase food production from existing farmland in ways that have a lower environmental impact and maintain the food production capacity over time. SI embraces a set of diverse agricultural technologies that share a common feature: their adoption is dependent on the interactions between farmers’ decision-making processes, locally specific agro-ecological conditions, and the traits of the technology itself. There are concerns about the sustainability of the maize mono-cropping systems that are in use in Laosc today. Therefore, we used discrete choice experiments (DCE) to explore the potential adoption or alternative agricultural systems. We analyse the heterogeneity of farmers’ preferences and willingness to pay for different cropping system attributes using a mixed logit model, and we discuss the possible drivers and barriers to the adoption of these more sustainable options. The results suggest the existence of four types of farmers: “fertility-minded”, “factor-constrained”, “maximisers”, and “risk-averse”. Each type of farmers was likely to react differently to the proposed sustainable intensification techniques. Overall, the DCE appeared to be an efficient tool to elicit the diversity of farmer preferences in an agricultural region and for fine-tuning strategies for successful research and development of sustainable intensification.

International audience

National audience; Is it possible to use nitrogen fertilization for weed control? Use of herbicides and mineral fertilizers must be reduced to make cropping systems more sustainable. These changes could lead to the development of a residual weed flora and an increased competition for resources, including nitrogen, between weeds and crops. This project aims at identifying which fertilization techniques and cultivar traits contribute to the biological regulation of weeds by modulating plant‐plant competition for nitrogen and thus help to reduce herbicide use, using a modelling approach (FLORSYS). The first step of the PhD project aimed at introducing plant‐plant competition for nitrogen into the FLORSYS model. FLORSYS already simulates competition for light and its role in crop growth and weed dynamics depending on cropping system, pedoclimate and species traits. In particular, an original function was proposed based on greenhouse experiments to estimate the nitrogen demand of individual plants from their leaf biomass irrespective of shading conditions. Then, virtual experiments were performed in a case study with maize monoculture, to identify the nitrogen fertilization techniques and the cultivar traits linked to nitrogen nutrition that impacted weed dynamics the most. Finally, innovative cropping systems will be proposed for this case study to promote biological weed regulation via nitrogen competition to reconcile weed control, crop production and biodiversity.; Est-il possible d'utiliser la fertilisation azotée pour lutter contre les mauvaises herbes ? L'utilisation d'herbicides et d'engrais minéraux doit être réduite pour rendre les systèmes de culture plus durables. Ces changements pourraient entraîner le développement d'une flore résiduelle de mauvaises herbes et une concurrence accrue pour les ressources, notamment l'azote, entre les mauvaises herbes et les cultures. Ce projet vise à identifier les techniques de fertilisation et les caractéristiques des cultivars qui contribuent à la régulation biologique des mauvaises herbes en modulant la concurrence entre les plantes pour l'azote et qui permettent ainsi de réduire l'utilisation d'herbicides, en utilisant une approche de modélisation (FLORSYS). La première étape du projet de doctorat visait à introduire la compétition plante-plante pour l'azote dans le modèle FLORSYS. FLORSYS simule déjà la compétition pour la lumière et son rôle dans la croissance des cultures et la dynamique des mauvaises herbes en fonction du système de culture, du pédoclimat et des caractéristiques des espèces. En particulier, une fonction originale a été proposée sur la base d'expériences en serre pour estimer la demande en azote de chaque plante à partir de sa biomasse foliaire, indépendamment des conditions d'ombrage. Ensuite, des expériences virtuelles ont été réalisées dans une étude de cas avec la monoculture du maïs, afin d'identifier les techniques de fertilisation azotée et les caractères des cultivars liés à la nutrition azotée qui avaient le plus d'impact sur la dynamique des mauvaises herbes. Enfin, des systèmes de culture innovants seront proposés pour cette étude de cas afin de promouvoir la régulation biologique des mauvaises herbes par la concurrence de l'azote pour concilier la lutte contre les mauvaises herbes, la production végétale et la biodiversité.

En Tunisie, la culture de blé dur en irrigué est pratiquée sur une superficie moyenne annuelle de 48 700 ha, soit environ les deux tiers des superficies céréalières conduites en irrigué. Elle produit en moyenne 180 000 t, soit 20 % de la production nationale de blé dur. Cependant, les rendements réalisés restent toujours en dessous des attentes avec une faible productivité, particulièrement celle de la ressource en eau. Dans ce contexte, l’objectif de ce travail est d’élaborer un diagnostic opérationnel de fonctionnement des exploitations céréalières irriguées et de mettre en exergue les principaux leviers d’amélioration des performances de la culture du blé dur. Pour ce faire, des enquêtes de terrain ont été menées auprès d’un échantillon de 698 céréaliculteurs. Les données recueillies ont permis d’élaborer une typologie de fonctionnement et d’analyser les performances de la culture du blé dur. Trois systèmes de production types ont été identifiés : un système monocultural basé sur la culture du blé dur, un système diversifié à orientation céréalière et un système diversifié à orientation maraîchère. L’analyse des performances a révélé une disparité nette entre deux niveaux de performance distincts pour chaque système de production. In Tunisia, irrigated durum wheat is grown on an average annual area of 48 700 ha, which represents two-thirds of the irrigated cereal area. It produces an average of 180 000 t, or 20% of national durum wheat production. However, the yields achieved are still below expectations with low productivity, particularly of water resources. In this context, this work aims to draw up an operational diagnosis of the irrigated cereal farms and to highlight the main levers for improving the performance of the durum wheat crop. To this end, field surveys were conducted with a sample of 698 grain farmers. The data collected made it possible to develop a typology of farming systems and to analyze the performance of the durum wheat cultivation activity. Three types of farming systems were identified: A monocultural system based on durum wheat cropping, a diversified cereal-oriented system and a diversified horticulture-oriented system. Performance analysis revealed a clear disparity between two distinct performance levels for each farming system.

International audience; The promotion of optimum rotations and agricultural management of winter wheat-based cropping systems is very critical, as wheat is considered an essential component in the Mediterranean diet. Considering the delicate economic situation of farmers in the Mediterranean area, recommending a low risk, sustainable farming system is desirable. In this study, an innovative application of a multi-criteria field-level approach is presented, targeting food security, farmer profitability and environmental sustainability. The CropSyst biophysical simulation model was calibrated and implemented for the study site. It was chosen for its agro-environmental robustness to simulate four rotations (wheat-wheat, wheat-fallow, wheat-potato, and wheat-fava bean). Four types of wheat agricultural management systems (full fertilization and full irrigation, full fertilization and zero irrigation, zero fertilization and full irrigation, and zero fertilization and irrigation) were tested in low and high soil water holding capacity (WHC) types. The effects of soil conditions, management practices and rotation type on wheat grain yields were assessed. Furthermore, the performance of each winter wheat-based cropping system was evaluated in terms of productivity (protein production and profitability) and the efficient use of resources (nitrogen and water), as well as the economic risk of low relative productivity each one engenders. The results show that there is no particular optimal scenario that can simultaneously ensure high productivity, reduce economic risk of low relative productivity, and achieve high wheat- water- and nitrogen-use efficiency. However, the wheat-fava bean rotation cultivated with no wheat fertilization appeared to be a better substitute to the wheat-wheat rotation in terms of protein production (0.93 t/ha versus 0.8 t/ha in low WHC soil and 1.34 t/ha versus 1.17 t/ha in high WHC). This cropping system achieved a higher net profit (2111 US$/ha versus 1222US$/ha in low WHC and 3550 US$/ha versus 2450 US$/ha in high WHC), showing high resource-use efficiency and was less risky for farmers. Moreover, a very high profit could only be attained with the wheat-potato rotation (8640 US$/ha and 12,170 US$/ha in low and high WHC, respectively), yet with low input-efficiency and high economic risk of low relative productivity.

Dossier Captages : Favoriser l'autoépuration; National audience

International audience; Cover crops are a potential component of agroecological cropping systems, since they may render crop rotations more sustainable. They simultaneously provide multiple ecosystem services, such as decreasing nitrate leaching, decreasing erosion, and increasing soil organic matter. However, cover crops increase evapotranspiration and reduce drainage, which results in a potential disservice for groundwater recharge. Little attention has focused on management of cover crop residues after destruction or their influence on water flux dynamics, particularly in dry and temperate climates. The objective of our study was to analyze and quantify the impact of cover crop management on soil water content and water flux dynamics to understand the main mechanisms of system functioning. We combined a two-year field experiment with crop-model simulations. We performed the field experiment in southwestern France that compared three cover crop treatments, with bare soil as the control. The treatments included (1) living cover crops lasting ca. 9 months from August-April, (2) crushing cover crops in November and leaving them as mulch on the soil, and (3) plowing up cover crops in November to promote residue decomposition and the green manure effect. The STICS soil-crop model was used to predict water fluxes that were not measured and to perform a 20-year independent simulation study based on recent climate series for the experimental site. Our main results indicated that cover crops (1) always reduce water drainage by 20-60 mm compared to that under bare soil; and (2) could significantly reduce soil water content (0-120 cm deep) for the next cash crop by a mean of 20-50 mm, and up to 80 mm in dry spring conditions, but early destruction could decrease this negative impact. The simulations clearly showed that the interaction between climate variability, i.e., rainfall distribution during the fallow period, and cover crop management should be considered to explain the impact of inter-annual variability on the water balance. Thus, destroying cover crops mechanically in late autumn and retaining the residues as mulch could be a good compromise between the multiple services the cover crop provides during the fallow period and avoiding the negative impact on soil water availability for the next cash crop.

Dossier Captage : Favoriser l'autoépuration; National audience

International audience; Background and aims: Agroforestry systems combining trees with crops or pastures have been widely used to reduce water, soil, and nutrient losses and associated water pollution from agricultural lands in both temperate and tropical regions. However, reviews on improvement/efficiency and the scope of such reductions by soil, management, climate, and hydrological processes are limited.Methods: This paper synthesized the available evidence on the reduction in surface runoff, soil erosion, nutrient, and pollutant losses (e.g., herbicides, pesticides, and antibiotics) to quantify the effectiveness of agroforestry systems on water quality improvement based on published studies.Results: On average, agroforestry systems reduced surface runoff, soil, organic carbon, and related nutrient losses by 1–100%, 0–97%, –175–92%, and –265–100%, respectively, with average values of 58%, 65%, 9%, and 50%, respectively. They also lowered herbicide, pesticide, and other pollutant losses by –55–100% (49% on average).Conclusions: Reduction efficiency of agroforestry systems is site-dependent and varies widely depending on different biophysical factors. A comprehensive science-based review is needed to generalize agroforestry design and site adaptability for water and soil conservation where climatic, geographical, ecological, and socio-economic conditions are relatively similar in the world.

Reducing pesticide use is a major challenge in agriculture and involves developing more sustainable methods that rely on non-chemical cropping techniques and biological regulations according to agroecological principles. Branched broomrape (Phelipanche ramosa (L.) Pomel) is a root parasitic plant which infects crops and causes dramatic yield losses worldwide. Managing broomrape is complex because it requires combining several cropping techniques whithin a global weed management strategy because broomrape is also able to infect non-parasitic weeds. The aim of this thesis was to stynthetize knowledge on branched broomrape dynamics in agroecosystems and to aggregate it within a mechanistic model in order to identify efficient management strategies from simulations. We synthetized knowledge from the literature, and acquired missing knowledge by setting up expriments (eg. mortality and dormancy of broomrape seeds) in order to model the complette life-cycle of branched broomrape. In order to predict the effects of cropping systems (crop succession and management plans) on broomrape dynamics and weeds in interaction, we connected our broomrape model to two existing models : a model of the effects of cropping systems on weed dynamics and a root growth model (roots being the infection site). The simulations allowed to identify promising combinations of techniques to control both broomrape and weeds, and revealed that weeds may regulate broomrape., Limiter l’usage de pesticides en agriculture est un enjeu crucial qui requiert de développer des méthodes plus durables, exploitant les techniques culturales non chimiques et les régulations biologiques, selon les principes de l’agroécologie. L’orobanche rameuse (Phelipanche ramosa (L.) Pomel) est une plante parasite des racines des cultures qui cause des pertes de rendement considérables dans le monde entier. Sa gestion est complexe car elle requiert de combiner plusieurs techniques culturales et elle doit intégrer la gestion des adventices non-parasites que l’orobanche est également capable de parasiter. L’objectif de cette thèse était de synthétiser les connaissances sur la dynamique de l’orobanche rameuse dans les agroécosystèmes et de les agréger dans un modèle mécaniste afin d’identifier des stratégies de gestion efficaces par simulation. Nous avons synthétisé les connaissances disponibles dans la littérature et acquis les connaissances manquantes par expérimentation (ex : mortalité et dormance des semences d’orobanche) afin de modéliser le cycle de vie complet de l’orobanche. Afin de prédire les effets des systèmes de culture (succession culturale, itinéraires techniques) sur la dynamique de l’orobanche et des adventices en interaction, nous avons couplé notre modèle orobanche à deux modèles existants : un modèle des effets des systèmes de culture sur la dynamique des adventices et un modèle de croissance racinaire (siège de l’infection). Les simulations réalisées ont permis d’identifier des combinaisons de techniques prometteuses pour gérer à la fois l’orobanche et les adventices, et montrent la possibilité de régulation de l’orobanche via les adventices.

Reducing pesticide use is a major challenge in agriculture and involves developing more sustainable methods that rely on non-chemical cropping techniques and biological regulations according to agroecological principles. Branched broomrape (Phelipanche ramosa (L.) Pomel) is a root parasitic plant which infects crops and causes dramatic yield losses worldwide. Managing broomrape is complex because it requires combining several cropping techniques whithin a global weed management strategy because broomrape is also able to infect non-parasitic weeds. The aim of this thesis was to stynthetize knowledge on branched broomrape dynamics in agroecosystems and to aggregate it within a mechanistic model in order to identify efficientmanagement strategies from simulations. We synthetized knowledge from the literature, and acquired missing knowledge by setting up expriments (eg. mortality and dormancy of broomrape seeds) in order to model the complette life-cycle of branched broomrape. In order to predict the effects of cropping systems (crop succession and management plans) on broomrape dynamics and weeds in interaction, we connected our broomrape model to two existing models : a model of the effects of cropping systems on weed dynamics and a root growth model (roots being the infection site). The simulations allowed to identify promising combinations of techniques to control both broomrape and weeds, and revealed that weeds may regulate broomrape., Limiter l’usage de pesticides en agriculture est un enjeu crucial qui requiert de développer des méthodes plus durables, exploitant les techniques culturales non chimiques et les régulations biologiques, selon les principes de l’agroécologie. L’orobanche rameuse (Phelipanche ramosa (L.) Pomel) est une plante parasite des racines des cultures qui cause des pertes de rendement considérables dans le monde entier. Sa gestion est complexe car elle requiert de combiner plusieurs techniques culturales et elle doit intégrer la gestion des adventices non-parasites que l’orobanche est également capable de parasiter. L’objectif de cette thèse était de synthétiser les connaissances sur la dynamique de l’orobanche rameuse dans les agroécosystèmes et de les agréger dans un modèle mécaniste afin d’identifier des stratégies de gestion efficacespar simulation. Nous avons synthétisé les connaissances disponibles dans la littérature et acquis les connaissances manquantes par expérimentation (ex : mortalité et dormance des semences d’orobanche) afin de modéliser le cycle de vie complet de l’orobanche. Afin de prédire les effets des systèmes de culture (succession culturale, itinéraires techniques) sur la dynamique de l’orobanche et des adventices en interaction, nous avons couplé notre modèle orobanche à deux modèles existants : un modèle des effets des systèmes de culture sur la dynamique des adventices et un modèle de croissance racinaire (siège de l’infection). Les simulations réalisées ont permis d’identifier des combinaisons de techniques prometteuses pour gérer à la fois l’orobanche et les adventices, et montrent la possibilité de régulation de l’orobanche via les adventices.

International audience

International audience; The Peruvian Amazon is undergoing rapid and uneven economic growth, alongside alarming rates of deforestation, increasing land use change and food security concerns. Although it has been widely acknowledged that food insecurity is intrinsically linked with deforestation, the links have not been thoroughly documented. The aim of this paper is to analyse the trade-offs and synergies between food security and forest exploitation at household level in mestizo communities in Ucayali, one of the regions with the highest deforestation rates in the Peruvian Amazon. To this end, 24 farmers were interviewed, surveys were conducted with a sample of 58 households, and an ad-hoc simulation modelling tool was developed and applied. Four main types of mestizo farming households were identified based on their crop and livestock diversity. For all farm types, the forest mainly represented a set aside area to support a potential increase in agricultural production. However, simulations showed that the different types of households, with different decision rules, lead to different rates of deforestation. The results of this study showed that the most diversified farming households presented the smallest trade-offs between food security and forest conservation, as they are the ones most likely to preserve the forest while ensuring their food security.

National audience

National audience

Agroforestry systems (AFS) are multi-species systems comprising cropped and associated spontaneous species, including trees. The species in AFS provide different levels of regulating, supporting and provisioning ecosystems services (ES). We assume that the provision of ES depends on the functional characteristics of all associated species and their spatial layout in the AFS, which we call here the “functional motif”. We propose the concept of Ecosystem Service Functional Motif (ESFM) defined as the smallest spatial unit that is relevant to understand the provision of all the targeted ES, at a given time. This ESFM is useful to determine the smallest scale at which data should be collected for relevant upscaling of AFS functioning. As a proof of the ESFM concept, we use it to describe existing AFS covering a wide range of species richness X spatial organisation. We show, for each AFS, the ESFM for various types of targeted (multiple) ES at various stages in the development of the system. We finally discuss the strengths and weaknesses of the ESFM concept for (i) analysing the AFS functioning, (ii) designing improved AFS according to ES targeted, and (iii) modelling such AFS.

Understory vegetation strips (UVS) are uncropped vegetation strips associated with tree rows in alley cropping agroforestry systems (Fig. 1). UVS are in appearance similar to other semi-natural habitats, such as field margins, which can constitute refugia for flora and fauna (Marshall & Moonen, 2002). To our knowledge very few studies have described the vegetation of UVS. Mézière et al., (2016) showed that 33% of the species present within UVS were never found in adjacent crop alleyways. However this result was restricted to only one field, in Southern France (Hérault). The purpose of this study was to confirm this result over more fields. Vegetation surveys were carried out in May 2017 in South-Western France over 16 winter cereal fields (8 alley cropping systems and 8 pure crop controls), either under conventional or organic management. The study revealed that UVS harboured richer, more even and more abundant floras – including species that are rarer in arable habitats – compared to crop alleyways and pure crop controls, especially under conventional management. Enhanced plant diversity at field scale is likely to have positive impacts on higher taxa that provide ecosystem services, such as pollinators and natural enemies.

National audience