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Dynamics of earthworm taxonomic and functional diversity in ploughed and no-tilled cropping systems
No full textInternational audienceNo-till has been proposed to limit the negative impacts of intensive agriculture. Soil organisms such as earthworms are good indicators of soil tillage effects. The aim of this study was to assess the dynamics of both taxonomic and functional diversity of earthworm communities after switching from ploughing i.e. deep tillage at 25–30 cm depth inducing soil inversion in this paper, to no-till. We assumed (i) that this transition led to increased diversity and (ii) that both taxonomic and functional indices indicated changes in tillage practices. Earthworms were sampled at three experimental sites in France on a Cambisol, a Luvisol, and a Fluvisol over several years (from 1995 to 2011), comparing both tillage systems. Standardized mean differences (Cohen’s indices) were calculated on several taxonomic and functional indices to quantify the influence of tillage practices within each site. We generally found a neutral or positive effect of the no-till on taxonomic and functional indices. The temporal responses of earthworm diversity were stronger in earliest stages (less than 6 years) than in oldest ones (more than 8 years) revealing transitory effects on diversity. In site III, for instance, a positive effect of no-till was observed on species and functional richness during the first 5 years but a negative effect was shown in year 6. Thus, no clear continuous increase of taxonomic and functional diversity was found in no-tilled fields, but positive and negative effects according to sites and years. More marked differences were found for taxonomic than for functional indices, suggesting that individuals settling the fields shared a similar combination of functional traits to those previously present. As transitory effects have been observed, this study highlighted that long-term trials are needed to assess the effects of cropping systems on earthworm biodiversit
Biotic and abiotic factors impacting establishment and growth of relay intercropped forage legumes
No full textIn organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services vary considerably depending on the forage legume biomass. The aim of this study was to identify factors that affect forage legume establishment and growth to help farmers adjust the management of the cover crop.Sixteen field experiments were conducted over a period of five years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L. After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Climatic conditions, and the accumulation of legume and weed biomass were monitored from when the legume was sown to destruction of the cover crop.Our results showed that a minimum threshold of about 500 kg ha−1 biomass in the aboveground parts of the cover crop was needed at the end of intercropping to obtain the minimum biomass of 2000 kg ha−1 in September necessary to guarantee ecological services. To obtain sufficient legume biomass at the end of intercropping period, a thermal time greater than 1900 °Cd and more rainfall than 300 mm are required for legume growth. Moreover, a legume density of at least of 300 plants per square meter at the wheat flowering stage was a good indicator of legume biomass at the end of the intercropping period. Rainfall was a limiting factor of legume growth between the end of the intercropping period and September.Legume density at wheat flowering and climatic conditions during the intercropping period thus appear to be good indicators to predict to capacity of cover crop to produce sufficient biomass in September. These indicators can be used by farmers as a management tool for the cover crop
Determination of tipping points for aquatic plants and water quality parameters in fish pond systems: A multi-year approach
No full textInternational audienceHigh levels of nutrients in fish ponds by fish farming may cause significant eutrophication leading to a loss in species richness and a decrease of cover of aquatic plants to phytoplankton dominance. This shift can be represented by a tipping point where a significant change in the state of the ecosystem is observed such as a change from high to low aquatic plants species richness and cover. A total of 100 fish ponds were studied during five years in the Dombes region, France, to determine tipping points in aquatic plant richness and cover using chlorophyll alpha (CHL), water transparency, Total N (TN) and Total P (TP) gradients with two statistical methods. The relationships between tipping points, nutrient loads and yearly variations in weather conditions were also evaluated. Looking at the five years data, tipping points were observed in aquatic plant richness at 6 and 60 mu g/l for CHL, and at 3.90 mg/L for TN concentration; as well as at 70 cm for water transparency, but no tipping point was found with TP. For aquatic plant cover, tipping points were observed at 11 mu g/L. for CHL, 2.42 mg/L for TN, 0.05 mg/L for TP, and at 62 cm for water transparency. These tipping points showed a significant decrease of aquatic plant species richness and cover, linked to the nutrient concentrations which drive the competition between the primary producers phytoplankton and aquatic plants. However, tipping points could vary significantly between years. The inter-annual variability may be due to an early occurrence of phytoplankton blooms in some ponds in a year preventing the establishment of aquatic plants, and thus influencing the value of tipping points. Weather conditions influence the competition between primary producers by impacting chlorophyll a and nutrients concentrations. When weather conditions supported increased nutrient concentrations, the development of phytoplankton and aquatic plants was facilitated and tipping points in aquatic plant richness and cover occurred with relatively high values. Thus, a significant decrease of plant cover and richness occurred at higher level of nutrients compared to the other years. In these cases, aquatic plants dominated over phytoplankton for the spring period, and also often during summer. In conclusion, tipping points observed are mainly linked to the competition between aquatic plants and phytoplankton. In shallow and eutrophic systems like fish ponds where nutrients are not a limiting resource, weather conditions act temporarily during spring as the main regulator of this competition
Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops
No full textInternational audience© 2015 Elsevier B.V. Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7tha-1). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5tha-1 whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (-12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species
Organic farmers’ motivations and challenges for adopting conservation agriculture in Europe
No full textInternational audienceConservation agriculture and organic farming are considered as promising sustainable agricultural system for producing food, while minimizing environmental impacts. Despite an increasing number of experimental data on organic conservation practices and various studies dealing with the adoption of conservation agriculture by farmers, none of those studies have specifically addressed conservation agriculture adoption under organic conditions in Europe. We carried out a survey with 159 farmers located in 10 European countries. These farmers had applied at least two of the following conservation practices: (i) no-tillage, (ii) reduced tillage and (iii) green manures. Each farmer assessed socio-economic, agronomic and environmental motivations and problems for each conservation practice, using a Likert scale. For each conservation practice, we ranked motivations and problems and carried out a principal component analysis, followed by clustering to identify groups of farmers. Independent of the conservation practices, the most important motivations were related to soil fertility preservation and challenges were mainly linked to crop management, machinery and yield performances. For all conservation practices, we identify three groups of farmers that shared the same type of motivations and challenges across Europe: “soil conservationists,” “agro-technically challenged farmers,” and “indifferent farmers.” Soil conservationist farmers were strongly motivated by soil preservation and minimizing environmental impacts. Agro-technically challenged farmers mainly expressed agronomic problems and challenges. There were no clear effects of location or farm characteristics explaining these attitudes, but they depended on farmers’ environmental concerns and beliefs. The study demonstrated that research priorities should address agronomic problems caused by the adoption of conservation practices in organic farming, weed control in particular
Agriculture biologique et protection de la qualité de l’eau : Cohérence des politiques publiques et dynamiques d’agriculteurs
No full textactes en lineNational audienceIn the light of the water policy, which is struggling to produce tangible results in terms of water resourcesquality, strong political signals have been sent following the Grenelle Environment Forum in 2009.Protecting water catchment areas (WCA) from agricultural diffuse pollutions has become a set objectivefor local authorities and catchment managers. Setting up water resource protection approaches impliesto initiate changes in agricultural practices and systems. Organic farming has been gradually recognizedas a relevant solution with regard to the drinking water issue and recent regulatory instruments conside that organic farming conversions may be preferentially located in WCAs. In this article we reviewed thefunctioning and the progress of WCA approaches, whose methodology was defined by the stateauthorities. We analysed the place reserved for organic farming in agricultural action programs, thevarious constraints affecting dynamics of organic conversions and determinants of success. Theseelements provide a critical understanding on the implementation of these public policies and the leversfor combining organic agriculture and issues related to protection of water resources.Face à une politique de l’eau qui peine à produire des résultats tangibles en termes de qualité de la ressource en eau, des signaux politiques forts ont été émis à la suite du Grenelle de l’environnement en 2009. Protéger les aires d’alimentation de captages (AAC) vis à vis des pollutions diffuses d’origine agricole est ainsi devenu un objectif fixé pour les collectivités territoriales et les gestionnaires de captages. Mettre en place des démarches de protection de la ressource implique d’initier des changements de pratiques agricoles et de systèmes. L’agriculture biologique (AB) a été progressivement reconnue comme une solution pertinente au regard de l’enjeu eau potable et les dispositifs réglementaires récents considèrent que les conversions en AB pourraient être préférentiellement localisées au niveau des AAC. Dans cet article, nous faisons un bilan du déroulement et de l’avancement des démarches AAC, démarches de projets dont la méthodologie a été définie par les instances de l’Etat. Nous analysons la place de l’AB au sein des programmes d’actions issus de ces démarches AAC, les diverses contraintes agissant sur les dynamiques de conversions en bio et les déterminants des réussites. Ces éléments portent un regard critique sur la mise en œuvre de ces politiques publiques et sur les leviers pour combiner agriculture biologique et enjeux liés à la protection de la ressource en eau
L’agriculture biologique comme réponse à la pollution de l’eau : apports de la géographie pour comprendre les dynamiques en cours
No full textThe conservation of water resources is a major issue in France because of the increasing problem of water pollution by nitrates and pesticides used in agriculture. In this context, organic farming is seen as a promising solution to this problem because of its Regulation that prohibits the use of chemical fertilisers and pesticides. In 2009, the Grenelle Law stated that priority should be given to organic farming in water catchment areas. This research aims at analysing why and how organic farming has been called in to tackle water pollution problems. It is based on a multi-level analysis. Firstly, the evolution over time of water and agriculture policies (as well as the sectorial paradigms that underly them) is analysed in order to understand how « organic farming » and « the protection of water ressources » came to be associated in public policies. Secondly, a case study is carried out to analyse how local stakeholders take up this idea in setting up projects aimed at developing organic farming toprotect water quality. Particular attention is paid to investigating the stakeholder networks andthe geographical scales at which the projects are implemented. Thirdly, social representations that farmers have of the water question and of organic farming are studied. To conclude, this work examines the contribution of geography to the understanding of an emerging feature: the place-based development of organic farming to tackle environmental problems. It creates new research perspectives related to the analysis of ecological transitions of agriculture, a topic that was so far largely ignored by geographers.Alors que les législations françaises et européennes fixent des objectifs ambitieux de protection de la qualité des eaux, les problèmes de pollution par les nitrates et les pesticides utilisés en agriculture persistent en France. Dans ce contexte, l’agriculture biologique qui n’utilise ni produits phytosanitaires ni engrais de synthèse, apparait de plus en plus comme une solution possible pour gérer ces problèmes « à la source ». Un objectif de développement de l’agriculture biologique dans les aires d’alimentation des captages en eau potable a ainsi été inscrit dans la loi Grenelle 1 en 2009. Cette thèse analyse pourquoi et comment l’agriculture biologique s’est trouvée convoquée pour répondre aux problèmes de pollution de l’eau. Elle repose sur une analyse multiniveaux des changements en cours, du niveau global de la conception des politiques publiques jusqu’à celui des agriculteurs, cible principale de cette politique en passant par le niveau territorial de mise en oeuvre de projets associant développement de l’agriculture biologique et protection de la qualité de l’eau. Dans un premier temps, l’évolution des politiques de l’eau et de l’agriculture et des référentiels sectoriels qui les sous-tendent est retracée afin de comprendre comment cette mise en relation entre « agriculture biologique et qualité de l’eau » a pu apparaitre dans l’action publique. Dans un second temps, une analyse de quatre projets territoriaux permet d’étudier comment les acteurs locaux se saisissent de cette convocation et s’engagent dans l’action. Une attention particulière est portée à l’analyse des réseaux d’acteurs impliqués et à celle de la diversité des échelles spatiales auxquelles les projets sont mis en oeuvre. Dans un troisième temps, ce sont les représentations qu’ont les agriculteurs de l’enjeu eau et de l’objectif de développement de l’agriculture biologique qui lui est associé qui sont étudiées. Notre discussion est consacrée aux apports des concepts et des méthodes de la géographie à la compréhension des dynamiques de développement territorialisé de l’agriculture biologique. Enfin, nous ouvrons des perspectives de recherche en termes d’analyse des transitions écologiques de l’agriculture, thématique qui a jusqu’ici été peu investie par les géographes
Les points de basculement dans les étangs piscicoles : Relation entre la qualité de l'eau et la biodiversité
No full textFish ponds are often enriched in nutrients in order to optimize the global productivity of ponds and increase fish biomass. High levels of nutrients in fish ponds due to fish farming may cause significant eutrophication leading to a loss in pond biodiversity and to phytoplankton dominance. This shift may be characterized by a critical threshold, a tipping point, where a significant change of species richness and/or abundance occurs for some taxonomic groups. Tipping points were studied in fish ponds in the Dombes and in the Forez areas, France. (1) Firstly, tipping points were analyzed in different taxonomic groups with three different statistical methods using five different diversity indices in order to evaluate best choices in the determination of tipping points. (2) Secondly, the multi-annual changes of tipping points in relation to nutrient loads, aquatic plants, and yearly variations in weather conditions were evaluated. (3)Then, tipping points of dragonfly richness were evaluated in relation to eutrophication gradients, aquatic plant richness and coverage, and fish production. (4) Finally, the effects of the different fish pond management practices such as fertilization, supplementary feeding, liming, and a dry year without water was evaluated on fish production, species richness of aquatic plants, and eutrophication. Our results showed that there is an important variation in tipping points following the statistical methods and the diversity indices used. In all taxonomic groups, aquatic plants were the most impacted by the eutrophication in fish ponds systems. The tipping points showed a significant decrease of aquatic plant species richness and cover, linked to nutrient concentrations which drive the competition between phytoplankton and aquatic plants. Therefore, the main valuable tipping points are linked to the switch from aquatic plant dominance to phytoplankton dominance. However, tipping points could vary significantly between years, mainly due to weather conditions in spring. In addition, dragonfly species richness and abundance showed to be negatively influenced by higher degrees of eutrophication. Tipping points were shown to be very important for the fish pond managers in order to keep an equilibrium state and thus provide fewer inputs as possible. A dry disturbance the most efficient practice to obtain a high performance of the fish production system: high fish production, high aquatic plant richness and low phytoplankton biomass. To reach a good ecological state, a good option seems to drain the fish ponds for once every four to five years. Consequently, it is therefore possible to predict with tipping points, when the equilibrium state of the pond will switch to phytoplankton dominance. Tipping points were thereby determined in order to maintain high aquatic plants richness and cover to preserve high biodiversity in fish ponds and high fish production.Les étangs piscicoles sont des milieux souvent enrichis en nutriments dans le but d’accroître la productivité global du système afin d’augmenter la biomasse de poisson. De fortes concentrations en nutriments peuvent entraîner une eutrophisation de l’étang conduisant à une perte de la biodiversité de l’étang et à une dominance du phytoplancton. Ce changement peut être caractérisé par un seuil critique, appelé point de basculement, où un changement significatif de la richesse en espèces et/ou de l’abondance survient dans plusieurs groupes taxonomiques. Les points de basculement ont été déterminés dans les étangs de la Dombes et du Forez. (1) Dans un premier temps, les points de basculement ont été déterminés dans différent groupes taxonomiques grâce à trois méthodes statistiques différentes en utilisant cinq indices de diversité, ceci afin d’évaluer les meilleures méthodes d’analyses. (2) Dans un deuxième temps, les changements pluriannuels des points de basculement ont été évalués en relation avec les concentrations en nutriments, les plantes aquatiques et les conditions météorologiques. (3). Par la suite, les points de basculements chez les Odonates ont été déterminés en relation avec des gradients d’eutrophisation du système, la richesse des plantes aquatiques et le recouvrement végétal, et la production piscicole. (4) Pour finir, le rôle des différentes pratiques piscicoles dans les étangs comme la fertilisation, l’addition de nourriture artificielle, le chaulage, et la mise en assec des étangs, a été étudié en relation avec la production piscicole, la diversité en espèces des plantes aquatiques, et l’eutrophisation du système. Nos résultats ont montré une importante variation des points de basculement suivant les différentes méthodes statistiques et les indices de diversité utilisés. Pour tous les groupes taxonomiques, les plantes aquatiques se sont révélées être les plus influencées par l’eutrophisation dans les étangs piscicoles. Les points de basculement ont montré une importante diminution de la diversité en espèces des plantes aquatiques et du recouvrement végétal, liés aux concentrations en nutriments qui dirige la compétition entre les producteurs primaires, à savoir le phytoplancton et les plantes aquatiques. Les points de basculement sont donc liés directement aux deux équilibres stables de dominance des plantes aquatiques ou du phytoplancton. Toutefois, les points de basculements peuvent varier significativement suivant les années, principalement due aux conditions météorologiques qui surviennent au printemps. De plus, la diversité en espèces et l’abondance des Odonates ont montré être négativement influencés par une trop forte eutrophisation du système. Les points de basculement sont très importants pour les gestionnaires des étangs qui pourront ainsi gérer leurs étangs de manière à garder un milieu équilibré et ainsi apporter le moins d’intrants possibles. Nos résultats ont ainsi montré qu’une mise en assec est la pratique permettant d’optimiser au mieux le système : productivité piscicole élevée, richesse des plantes aquatiques élevée et faible concentration de chlorophylle α. Ainsi, pour atteindre un bon état écologique de l’étang, une mise en assec des étangs doit s’effectuer toutes les quatre à cinq ans. Par conséquent, il est ainsi possible de prédire grâce aux points de basculement, le moment où l’état d’équilibre de l’étang va basculer vers une dominance phytoplanctonique. Des points de basculement ont ainsi été déterminés dans le but de maintenir une forte diversité de plantes aquatiques et un fort recouvrement végétal, pour préserver une forte biodiversité des étangs et une bonne productivité piscicole
Ecological embeddedness in animal food systems (re-)localisation: A comparative analysis of initiatives in France, Morocco and Senegal
No full text[Departement_IRSTEA]Territoires [TR1_IRSTEA]DTAM [Axe_IRSTEA]DTAM3-ECOPRAInternational audienceLocalised animal food systems tend to be perceived as more environmentally sustainable than non-localised systems. However, these initiatives span a diverse array of projects, and the way ecological issues are considered may vary greatly depending on the actors and systems involved. With re-localisation of food chains considered a way of fostering sustainable development, this diversity should prompt a closer look at the real environmental dimension of sustainable development through livestock farming. In order to understand better how food system re-localisation trends can support environmentally sustainable development, this paper analyses the importance and place that the environmental issues may hold in localised animal food systems. We mobilize the concept of ‘ecological embeddedness’ to help consider how, why and to what extent natural environment influences development and shapes relationships between agents within food networks. We use the analytical framework developed by Morris and Kirwan (2011) to compare five initiatives designed to differentiate animal food products by linking their qualities to the place of production in three countries: France, Morocco, and Senegal. The comparison of the way food-systems stakeholders understand, realise, utilise, and negotiate the ecological dimensions of food production shows three different forms of ecological embeddedness depending on the way the ecological dimensions of production are linked with environmental protection issues. The first form corresponds to the Moissac case in which practices linked with ecology are very consciously highlighted as environmentally-friendly practices. The second form reflects cases in which environmentally-friendly practices and values associated to ecology exist and are highlighted through their impact on products quality, not as participating in environment protection. The third form concerns the Senegalese case in which food systems seem to be engaged in a process of ecological ‘dis-embeddedness’. Finally, the comparison of different cases underlines the non-systematic coexistence between Localised Food Systems and ecological embeddedness. The “broad” systemic approach adopted here also unlocks insight into the ecological embeddedness of food systems. This analysis of collective initiatives involving different stakeholders led to consider the roles they can play in shaping the ecological embeddedness of the livestock food systems