Portail Hal-l'Institut Agro Rennes-Angers
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Choreographing rhizosphere effect with agricultural practices for agroecology?
No full textInternational audienceFor sustainable agriculture, soil-plant interactions (i.e., the rhizosphere effect) is prominent focus, since they determine plant health and nutrition. However, system-level agricultural management practices interfere with the rhizosphere effect. In this study, we characterized the rhizosphere effect of winter wheat (Triticum aestivum var. LG Absalon) on farm fields along two levels of crop diversity induced by rotation (high or low) combined with two tillage intensities (conventional or reduced).The rhizosphere effect was determined from differences in enzyme activities involved in carbon (β-glucosidase), nitrogen (arylamidase) and phosphorus (acid phosphatase) cycles measured in the rhizosphere and bulk soil. We observed positive rhizosphere effects for all enzymes, but they were significantly altered by soil tillage. High temporal diversification and reduced tillage increased the intensity of the rhizosphere effect for all enzymes studied, suggesting the relevance of agroecological management of arable land to promote nutrient cycling. In contrast, benefits of crop diversification on the rhizosphere effect decreased drastically under conventional tillage.Accordingly, the rhizosphere effect should be carefully synchronize with agricultural practices under agroecological transition
One-time application of controlled-release blended fertilizer increases rice yield and nitrogen utilization by optimizing root morphological trait distribution and nitrogen uptake
No full textInternational audienceOne-time application of controlled-release blended fertilizer (CRBF, a mixture of five nitrogen (N) fertilizers in a certain ratio) can achieve high yield and N use efficiency (NUE) in rice (Oryza sativa L.). However, the effects of CRBF with one-time application on root spatial distribution and physiological characteristics remain unclear. We measured the effects of CRBF with one-time application on rice yield, NUE, root morphology and growth, and N uptake capacity in field and root box experiments. Six N treatments were set up: no nitrogen (N0), high-yield three-split application of urea as a control (CK), urea (U) with broadcast, U with side-deep fertilization, CRBF with broadcast, and CRBF with side-deep fertilization. Our findings showed that root characters were positively correlated with yield and NUE. Compared to CK and U treatments, CRBF with one-time applications increased root characters (including root biomass, root N uptake, root activity, and the expression level of ammonium transporters) at tillering and heading stages. The root length, surface area and volume in the 0–10 cm soil layer enhanced under CRBF with one-time applications at tillering stage, and in the 0–20 cm soil layer at the heading stage. This contributed a 5.96 %–39.40 % and 3.69 %–16.87 % increase in plant dry matter accumulation and N uptake, and a 2.08 %–18.28 % and 14.60 %–149.57 % increase in yield and NUE, in 2022 and 2023, respectively. Taken together, our findings showed that one-time application of CRBF could increase rice yield and NUE by optimizing the root morphology distribution and N uptak
Sulfur nutrition modifies the response of Medicago truncatula genotypes to nitrate supply during seedling pre-emergence growth
No full textInternational audienceLegumes produce protein-rich seeds and have been cultivated for centuries to feed humanity and livestock. Despite their ability to fix dinitrogen, seedlings are sensitive to nitrogen availability before symbiosis establishment. In the past years, our team has been working on seedling pre-emergence (i.e. heterotrophic) growth with and without nitrogen source, using a broad panel of accessions of barrel medic (Medicago truncatula), a model legume plant. In other Legumes like pea, sulfur metabolism appears to be critical during germinative and post-germinative events. Thus, we assume sulfur nutrition may influence seedling growth properties of genotypes. The present study focuses on the genotypic variability on a selection of accessions of M. truncatula during the heterotrophic growth, under different nutrient conditions, including sulfate availability. We determined traits associated with seedling performance (seed biomass use and organ elongation) to characterize phenotypic variations in response to contrasting nitrate and sulfate conditions. The study reveals that genotype response to nitrate deficiency is influenced by sulfate availability, the genotype × nutrient conditions interaction being more or less pronounced depending on the trait. Elemental, isotopic and inorganic anion analyses of seeds and seedling organs also reveal genetic variability and highlight genotype x nutrient conditions interaction, suggesting differential N/S metabolic interactions amongst accessions
Mesoscale assemblages of fish and megainvertebrates as evidence of benthiscapes on continental shelves
No full textInternational audienceDespite the relatively small proportion of ocean surface they represent, continental shelf ecosystems are among the most productive in the world. Located at the interface between terrestrial and marine environments, these habitats are structured by strong environmental forcings, especially on the sea bottom. A clear understanding of the spatial distribution of these habitats, along with knowledge on the composition and functioning of their associated communities, is essential for fisheries management and ecosystem conservation. Here, we used data from yearly EVHOE otter trawl surveys (2008-2020) to characterize the spatial structuration of benthic communities of the entire continental shelf of the Bay of Biscay (France), and to investigate the potential environmental drivers of these patterns. Two separate biological components were studied: epibenthic megainvertebrates and bentho-demersal fish. Clustering analyses identified seven assemblages from species composition of stations. Each assemblage was denominated according to its geographical location. We detected a strong correlation between the spatial organization of the different assemblages identified for fish and megainvertebrates, providing evidence for broad-scale spatial structuration of benthic habitats-benthiscapes-in this shelf ecosystem. The most influential environmental variables were identified as bottom temperature, sediment type, and primary production. Patterns in certain structural parameters, such as biomass, revealed possible spatial differences in ecological functioning. For example, we observed a drop in biomass from the coast to the central part of the shelf, followed by an increase in biomass near the edge of the Armorican shelf. These patterns reflect major large-scale processes (river inputs versus shelf-break upwelling) structuring the entire Bay of Biscay ecosystem. A comparative analysis revealed that the biological features and functioning observed in this study are shared with other European continental shelves. In addition to improving our knowledge of benthic environments, studies such as this one can promote improvements in ecosystem-based management and marine spatial planning of a fast-changing ecosystem under multiple anthropogenic stresses
Modelling the impact of hypoxia on critical essential fish habitats throughout the life cycle of exploited marine species
No full textInternational audienceSpawning grounds and juvenile habitats are critical essential fish habitats (CEFH) facing multiple anthropogenic pressures. Yet the impacts of these pressures on fish population dynamics are poorly quantified. In this study, we address the impact of hypoxia on CEFH and its consequences on the productivity of exploited marine fish populations. Our approach relies on an age-and stage-structured simulation model, including habitat effects on egg, juvenile, or spawner mortalities to integrate the impact of hypoxia on spawning and juvenile habitats. We applied this framework in the Baltic Sea (BS) to explore population responses of cod, plaice, and herring, which face hypoxic conditions in their CEFH. All scenarios lead to modifications in fishing mortality, population size, and yield at maximum sustainable yield, but with different magnitudes depending on the impacted life stage. Perturbations of spawning habitats that result in higher mortality of eggs had the least impact, while the more direct effect on spawners themselves had the largest impact. Within each scenario, the responses also depended upon species and life history traits, with contrast in steepness and lifespan that explain most of the differences between species. Cumulative impacts of pressures in both CEFH were also in vestig ated and revealed mainly nonadditive responses. Our framework is a generic tool, transferable to a large panel of case studies, to quantify the relative impact of CEFH degradation/restoration for the dynamics of marine exploited populations
Economic performance of organic dairy farms during and after conversion
No full textInternational audienceEmpirical research on the economic performance of organic farming yields conflicting results. The findings vary by region, agricultural sector, economic performance indicators, and methodologies used. This study compares the economic and financial performance of conventional and organic dairy farms by specifically examining the performance trends during the period when conventional farms got converted into organic farms. Using a difference-in-differences estimator within a panel regression model, we analysed the microdata of 1,016 farms in Ille-et-Vilaine (Brittany, France) between 2007 and 2018, including 62 farms that had converted from conventional farming to organic farming during this period. Our results show that, contrary to expectations, the financial performance of the farms did not reduce significantly during the conversion. However, after the two-year conversion period, the profitability and return on assets of organic farms exceeded those of conventional farms. Considering the limited sample size of organic farms analysed in this study, these findings require further validation
Effet de la granulation sur l'utilisation digestive et métabolique de l'énergie d'aliments formulés à partir de blé, de maïs ou d'orge chez le porc
No full textInternational audienceEffects of pelleting on digestive and metabolic use of energy from diets containing wheat, maize and barley in pigsFeed is commonly pelleted in feed mills but without considering consequences on the digestive and metabolic use of energy by growing pigs. The objective of this study was to determine effects of pelleting on ileal and faecal digestibility and metabolic use of energy in growing pigs when three diets were formulated using wheat, maize or barley as main ingredients. The diets were fed as mash or pellets. Ileal digestibility was measured for seven pigs that had received an ileo-rectal anastomosis. Faecal digestibility and net energy were measured for 30 pairs of pigs housed in a respiration chamber. Pelleting significantly increased the ileal digestive use of energy (+3.0, +3.9 and +1.9 percentage points for wheat, maize and barley, respectively) by increasing the digestibility of starch (+1.6 percentage points). Based on the faeces, the digestive use of energy also increased significantly, but to a lesser extent. At a metabolic level, the improvement in digestive use induced by pelleting (mean of +0.34 MJ of digestible energy per kg of dry matter for the three diets) was not completely recovered in the net energy of the diet (mean of +0.32 MJ of net energy per kg of dry matter). This suggests that pelleting may also change the metabolic pathways involved in nutrient use, thus decreasing efficiency.</p
Biochars improve agricultural production: The evidence base is limited
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On-farm water quality: Co-design of result-based indicators
No full textInternational audienceCONTEXT: Pollution of water resources by substances emitted by agriculture, such as nitrate, pesticides, pharmaceutical residues, fecal microorganisms and microplastics, remains a crucial issue. To assess the effectiveness of pollution-mitigation projects, water quality is usually monitored at the watershed scale. In parallel, farmers and agricultural advisors use mainly means-based indicators to assess farm sustainability. In Brittany, France, the Terres de Sources project addresses the following issues: (i) individual farmers cannot assess effects of changes in their practices using result-based water-quality indicators at the watershed outlet and (ii) means-based indicators provide little information about local water quality.OBJECTIVE: The aim of this project was to gather together researchers, farmers and advisors to build operational result-based indicators that would allow farmers to estimate on-farm emissions of pollutants to water. This article highlights the implementation and outputs of a collective design process to create such indicators.METHODS: The Knowledge-Concepts-Proposals design method was implemented to explore ideas around the initial concept of “result-based water-quality indicators at the farm scale”. The method’s design process has four steps, from initiation to outputs. Emerging ideas of indicators were classified in four categories and we finally selected scientifically relevant and achievable indicators. The methods for measuring these indicators were worked during the final phase of the design process.RESULTS AND CONCLUSIONS: The main results of the design process were (i) a set of result-based indicators focused on nitrate and pesticides and related to chemical measurements and bioindicators, (ii) the development of phases of “farm characterization” and “on-farm monitoring strategy” to understand water circulation, the relevant “types of water” to sample and suitable on-farm monitoring locations. In addition, breakthrough ideas have emerged but not exploited in this project; they were related to indicators based on senses and on exposure of livestock to pollutants. Despite fixation effects, the group was actively involved in the design process and in the proposal of subsequent prototype testing on farms.SIGNIFICANCE: Most of the indicators selected had already been developed at the watershed scale, but attempting to adapt them to the farm scale was an originality. Farm-scale studies help understand sources of pollutant emissions that decrease water quality. Farmers’ use of comprehensive assessment tools would help encourage them to pursue their efforts in agroecological transition
Un kit pédagogique pour sensibiliser à l’approche globale et l’ergonomie à la traite
No full textinclus dans une série de webinaire de restitution des résultats du Casdar IP Ergo'TraiteWebinaire de présentation de résultats sur les besoins de sensibilisation autour des facteurs agissant sur les conditions de travail des éleveurs et éleveuses en bovins lait atour de la traite, présentation d'un kit pédagogique de sensibilisation sur la traite durable a destination des futurs trayeur