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Based on discussions in a workshop associated with the conference The Agroecological Imagination: A Franco-American Exchange, we synthesize the state of agroecological education. We focus on three ...

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones.

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. 0.7 t ha −1 ). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha −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.

The use of the perennial grain intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth &amp, D.R. Dewey) may have the potential to sustain soil health and fertility through the development of an extensive root system. However, references are scarce to demonstrate its potential influence in a context of a limited perennial grain growth phase, integrated into annual grain crops succession. This study aims at determining how early a perennial crop rooting system differs from that of an annual crop through root development and root traits and microbial indicators. Our results indicate that the two-year-old intermediate wheatgrass promotes a denser and deeper rooting system with proportionally more root biomass and length deeper in the soil profile. From the first growing season, the perennial grain demonstrated a suite of root traits typical of a more resource-conservative strategy, and more belowground-oriented resource allocation. Soil fungal biomass indicators were enhanced. Arbuscular mycorrhizal fungi (AMF) indicators were notably found to be improved at 1 m depth during the second growing season. This study provides evidence that grain-based agriculture can benefit from the potential of deeper and long-lived root systems of intermediate wheatgrass to manage soils. The periodic use of a short-term perennial phase in the crop rotation has the potential to improve soil functioning in the long term.

International audience; Sustainable cropping systems that balance agricultural productivity and ecological integrity are urgently needed. Overreliance on soil tillage and herbicides to manage weeds has resulted in a number of major environmental problems including soil erosion and degradation, biodiversity loss, and water quality impairment. Combining organic farming and conservation agriculture is a viable alternative to address these challenges. In particular, mulch-based no tillage systems can be used to reduce tillage in organic production, improving soil quality while decreasing labor and fuel requirements. This technique involves planting cash crops directly into terminated cover crops that remain on soil surface and serve as mulch to prevent weeds establishment and protect soil from erosion. Despite potential benefits, adoption of organic mulch-based no tillage is limited due to challenges with cover crop termination, weed suppression, and yields. Here, we (i) review international research on organic mulch-based no tillage systems (soybean and maize), (ii) identify production issues that limit the success of this technique, and (iii) outline research priorities. As result, organic mulch-based no tillage is knowledge intensive and requires advanced planning and careful management of the cover crop. Primary challenges include timely cover crop establishment and termination, nutrient management, reduced soil temperature and moisture at planting, and achieving adequate seed-to-soil contact when planting into thick mulch on soil surface. Long-term research is needed to better understand the effects of this technique production on soil health and on the broader environmental and economic impacts. To increase adoption of organic mulch-based no tillage, future research should focus on (i) screening species and cultivars to identify cover crop and crop combinations that optimize cropping system performance and (ii) developing equipment for improving cover crop termination and seed placement. Research conducted in partnership with farmers will be valuable for developing guidelines and increasing adoption of this technique.

Nitrogen (N) deficiency and weed infestation are the main factors limiting the yield and quality of organic soft winter wheat (Triticum aestivum L.). If forage legumes are associated with wheat, simultaneously or successively, they can help to reduce the impact of limiting factors through the ecological services they provide. The aim of this study was to evaluate two intercropping strategies to increase soft winter wheat yield and protein content and improve the provided ecological services (mainly N provisioning and weed control) by white clover (Trifolium repens L.). White clover (Trifolium repens L. cv Aberdai) was intercropped with soft winter wheat (Triticum aestivum L. cv Renan) under organic conditions. Two strategies were compared, simultaneous intercropping versus relay intercropping using three field experiments. A control treatment with sole wheat crop was included in the three field experiments. Fertilization management on organic wheat was also tested (0 versus 100 kg N applied at spring time) to evaluate its incidence on cash and cover crop yields and protein content. White clover shoot dry matter (DM) was significantly higher in simultaneous intercropping compared to relay intercropping at wheat harvest (2.2 vs. 0.1 Mg DM ha−1) and at cover destruction (4.5 vs. 3.1 Mg DM ha−1). Wheat grain yield was not affected by the intercropping strategy while the protein content was significantly lower under simultaneous intercropping system (9.1% of the grain DM) compared to relay intercropping or in wheat as sole crop (10.0% of the grain DM). At cover destruction, both simultaneous and relay intercropped white clover significantly decreased weed shoot DM compared to sole wheat crop (−1.4 Mg DM ha−1 for relay intercropping and −1.8 Mg DM ha−1 for simultaneous intercropping). In comparison to relay intercropping strategy, N accumulation in white clover shoot DM was higher under simultaneous intercropping strategy at wheat harvest (52 vs. 2 kg N ha−1) and at cover destruction (123 vs. 83 kg N ha−1). In conclusion, our study has highlighted the positive effect of combining a simultaneous intercropping strategy with high N availability to guarantee a sufficient level of legume shoot DM as rapidly as possible to increase both N accumulation and weed control services, thus reducing the risk of impairing winter wheat yield and protein content.

International audience; Controlling groundwater diffuse pollution induced by agricultural practices remains a significant challenge and has been receiving strong attention in the European Union (EU) for the last 25 years. The EU's Nitrates Directive (91/676EC) and its associated Nitrate Vulnerable Zone (NVZ) legislation were recently revised in France in 2015, requiring farmers to adopt measures and then modify their agricultural practices to protect water resources. Yet these measures are not always implemented in an optimal way, thus limiting improvement of groundwater quality. Based on semi-directive interviews with 14 French farmers, we developed an innovative farm-scale method composed of four steps. First, we described how these farmers implemented Nitrate Directive measures. Second, we evaluated their impact on farm structure and third their consistency with farmer's strategy. Fourth, we assessed their suitability for farm management as an integrative analysis of the previous step. Through this approach, we identified 3 types of farm management. A group of "Beyond Regulation" composed of farmers for whom Nitrate Directive measures are suitable for their farm management. They optimally implement these measures to reduce pressure on groundwater quality. For the second group named "Soft Regulation-constraints", Nitrate Directive measures are less suitable for their farm management because they have another lucrative activity than cash crop production. This group could benefit from a redesign of the measures, changing from means- to result-oriented obligation in order to take into account the local conditions and also their farm management constraints. For the third group, denoted as "Strong Regulation-constraints", ND measures are not suitable for their farm management. The way they implement measures is usually not optimal to reduce pressure on groundwater quality. We suggest that, investing in an "action-learning" program for such farmers could make them understand the usefulness of this regulation and help them to make the measure implementation suitable for their farm management. This farm-scale method could be used further for water management stakeholders to (i) evaluate the suitability of measures from Water Policy for the diversity of farm management or (ii) design suitable measures for the diversity of farm management on a territory subjected to groundwater pollution issue.

Western European agriculture is largely defined by the high level of productivity of its cereal grain production. Such productivity is largely a result of farm specialization and intensification. This approach however has led to environmental problems and farm sensitivity to climatic and economic hazards. Recently, perennial grains have been promoted as a potential alternative, particularly with intermediate wheatgrass (Thinopyrum intermedium). Perennial grains bring new perspectives and innovation, and can contribute to both system diversification and environmental performance. Above all, the value of year-round ground cover and root activity, as well as the ability to harvest both grain and forage production, offers a large range of interest and potential application for such a grain crop. Realization of the potential benefits from perennial grains depends on the development of suitable seed material and the identification of tangible economic and environmental benefits coming from the integration of perennial grains into crop rotations. Although more work is needed, perennial grains are compatible with the current European interests and policies for food security, soil health, water quality, and farmer interest in innovative practices and sustainable cropping systems.

In organic farming, weeds are one of the threats that limit crop yield. An early prediction of weed effect on yield loss and the size of late weed populations could help farmers and advisors to improve weed management. Numerous studies predicting the effect of weeds on yield have already been conducted, but the level of uncertainty about weed effect is expected to be very high in organic crops. It is thus more appropriate to provide farmers and advisors with distributions of possible production levels, rather than with point values. The purpose of this study was to estimate the effect of early weed density at the end of the tillering stage of organic winter wheat on subsequent yield and on late weed density at flowering, by using quantile regression. Results showed that this method can be applied to a hyperbolic model and to an allometric density-dependent model, to describe the distribution of yield values and of late weed density respectively, as functions of early weed density measurements. Mechanical weed control showed no significant effect on the relationship between early weed density and grain yield, but it decreased late weed density. Yield and late weed density distributions derived by quantile regression provided sound information on the possible effect of weeds on organic winter wheat production.

In 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.

The interest of organic farmers in adopting conservation agriculture principles, including minimal soil disturbance, permanent soil cover and crop rotation has been growing since the early 2000s. However, currently there is no network for organic farmers practicing conservation agriculture, and a lack of knowledge on how organic farmers implement conservation agriculture in practice. Consequently, few technical references are available for organic farmers when they start applying conservation agriculture practices, in particular on controlling weeds without the use of herbicides. The main objectives of this study were: (1) to explore the diversity of conservation agriculture techniques (i.e., reduced tillage, no-tillage and green manures) practiced among European farmers, and (2) to identify farmers’ main strategies for implementing conservation agriculture and the agronomic and environmental factors that determine these strategies. Strategies were identified by analyzing survey results on: (1) the type and degree of use of conservation agriculture practices by farmers, and (2) the effects it produces in terms of soil disturbance and soil cover (low, medium and high). We carried out a survey of 159 European organic farmers and collected 125 data sets on management of winter-sown crops. Among the conservation agriculture practices, reduced tillage was used by 89%, no-tillage by 27% and green manure by 74% of the 159 interviewed farmers. Green manures were more frequently used in northern Europe than in the south (below 45°N). Most of the farmers used crop rotations, with a mean duration of 6 years. A wide diversity of conservation agriculture practices were used, with farmers rarely using all three techniques (no-till, reduced till and green manures) within one system. The range of practices was grouped into five strategies ranging from intensive non-inversion tillage without soil cover to very innovative techniques with no-tillage and intercrops. The five strategies for conservation agriculture could be grouped into two larger categories based on weed control approach: (1) intensification of the mechanical work without soil inversion or (2) biological regulation of weeds with cover crops. The diversity of strategies identified in this study shows that organic farmers use innovative approaches to implement conservation agriculture without herbicides. This study's findings will help organic farmers to experiment with innovative practices based on conservation agriculture principles and also benefit conventional farmers who use conservation agriculture practices and would like to reduce or eliminate the use of herbicides.

In 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 can vary considerably depending on the growing conditions. The aim of this study was to identify early indicators to assess these two ecological services, thereby giving farmers time to adjust the management of both the cover crop and of the following crop. Nine field experiments were conducted over a period of three 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 Two levels of fertilization were also tested (0 and 100 kg N ha(-1)). After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Legume and weed biomass, nitrogen content and accumulation were monitored from legume sowing to cover destruction. Our results showed that a minimum threshold of about 2 t ha(-1) biomass in the aboveground parts of the cover crop was needed to decrease weed infestation by 90% in early September and to ensure weed control up to December. The increase in nitrogen in the following maize crop was also correlated with the legume biomass in early September. The gain in nitrogen in maize (the following crop) was correlated with legume biomass in early September, with a minimum gain of 60 kg N ha(-1) as soon as legume biomass reached more than 2 t ha(-1). Legume biomass in early September thus appears to be a good indicator to predict weed control in December as well as the nitrogen released to the following crop. The indicator can be used by farmers as a management tool for both the cover crop and following cash crop. Early estimation of available nitrogen after the destruction of the forage legume can be used to adjust the supply of nitrogen fertilizer to the following crop.

International audience; AbstractReduced tillage is increasingly promoted to improve sustainability and productivity of agricultural systems. Nonetheless, adoption of reduced tillage by organic farmers has been slow due to concerns about nutrient supply, soil structure, and weeds that may limit yields. Here, we compiled the results from both published and unpublished research comparing deep or shallow inversion tillage, with various categories of reduced tillage under organic management. Shallow refers to less than 25 cm. We found that (1) division of reduced tillage practices into different classes with varying degrees of intensity allowed us to assess the trade-offs between reductions in tillage intensity, crop yields, weed incidence, and soil C stocks. (2) Reducing tillage intensity in organic systems reduced crop yields by an average of 7.6 % relative to deep inversion tillage with no significant reduction in yield relative to shallow inversion tillage. (3) Among the different classes of reduced tillage practice, shallow non-inversion tillage resulted in non-significant reductions in yield relative to deep inversion; whereas deep non-inversion tillage resulted in the largest yield reduction, of 11.6 %. (4) Using inversion tillage to only a shallow depth resulted in minimal reductions in yield, of 5.5 %, but significantly higher soil C stocks and better weed control. This finding suggests that this is a good option for organic farmers wanting to improve soil quality while minimizing impacts on yields. (5) Weeds were consistently higher, by about 50 %, when tillage intensity was reduced, although this did not always result in reduced yields.

Conservation 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.

In agriculture, differences between the kinetics of crop requirements and the rate of soil mineralization are known to affect wheat yield and quality. The high cost of organic nitrogen fertilizer may result in nitrogen availability being a limiting factor during the crop cycle. It is therefore necessary to improve fertilizer application conditions, to limit losses, to ensure that grain quality exceeds a certain threshold, and to optimize economic efficiency. The aim of this study was to improve nitrogen management in organic winter wheat crops by optimizing spring fertilization. We validated and used the Azodyn model [Eur. J. Agron. 10 (1999) 129] to determine the effect of various fertilization strategies on winter wheat production under N constraints. We first adapted the Azodyn model by constructing an organic fertilizer submodel. The resulting Azodyn–Org model was tested under several sets of conditions for the rate and timing of organic fertilizer applications, in three experiments. Preliminary results confirmed that the Azodyn model accurately predicted N soil availability in a wide range of conditions. We assessed the performance of the Azodyn–Org model for predicting grain yield, grain protein content and mineral N in the soil. We found that grain yield was correctly predicted whereas grain protein content was slightly overestimated. Thus, the Azodyn–Org model has potential for use as a decision-making tool for managing spring N fertilization in organic wheat crops.

International audience; Organic farming systems are often nutrient-limited. Moreover, even if organic guidelines emphasize the reliance on ecological processes and recycling, the trend towards farm specialisation induces an increased reliance on off-farm fertilising materials in arable areas. There is, therefore, a need to better understand the drivers of nutrient inflows on organic farms. Our objectives were to assess the nitrogen (N,) phosphorus (P) and potassium (K) farm-gate inflows through fertilising materials, and the nutrient budget and use efficiency over a large range of organic farming systems. To do this, 56 interviews with organic farmers concerning their nutrient management for the years 2010 and 2011 were carried out in 2012 in three French agricultural districts distributed over a gradient of farming activity. The results showed that the farm-gate fertilising material inflows were strongly related to both the ratio of land under cereal and oilseed crops (proxy of nutrient ‘demand’) and the stocking rate (proxy of nutrient ‘supply’). However, other inflows (biological N fixation, feed use, fodders and straws) increased with the stocking rate, leading to low farm-gate N and K use efficiency (0.2 and 0.7, respectively) on livestock farms compared to arable, stockless farms (1.4 and 3.5, respectively). Such results helped to disentangle the drivers of nutrient use in organic farms compared to previous analyses based solely on farm production typology.

In organic grain production, weeds are one of the major limiting factors along with crop nitrogen deficiency. Relay intercropping of forage legume cover crops in an established winter cereal crop might be a viable option but is still not well documented, especially under organic conditions. Four species of forage legumes (Medicago lupulina, Medicago sativa, Trifolium pratense and Trifolium repens) were undersown in six organic wheat fields. The density and aerial dry matter of wheat, relay-intercropped legumes and weeds were monitored during wheat-legume relay intercropping and after wheat harvest until late autumn, before the ploughing of cover crops. Our results showed a large diversity of aerial growth of weeds depending on soil, climate and wheat development. The dynamics of the legume cover crops were highly different between species and cropping periods (during relay intercropping and after wheat harvest). For instance, T. repens was two times less developed than the other species during relay intercropping while obtaining the highest aerial dry matter in late autumn. During the relay intercropping period, forage legume cover crops were only efficient in controlling weed density in comparison with wheat sole crop. The control of the aerial dry matter of weeds at the end of the relay intercropping period was better explained considering both legumes and wheat biomasses instead of legumes alone. In late autumn, 24 weeks after wheat harvest, weed biomass was largely reduced by the cover crops. Weed density and biomass reductions were correlated with cover crop biomass at wheat harvest and in late autumn. The presence of a cover crop also exhibited another positive effect by decreasing the density of spring-germinating annual weeds during the relay intercropping period. (C) 2013 Elsevier B.V. All rights reserved.

Wheat yields and grain protein content are lower and more variable in organic conditions than in conventional agriculture, mainly due to nitrogen (N) deficiency and weed competition. The undersowing of legume cover crops in growing winter wheat, also known as relay intercropping, is assumed to be a proficient way of enriching the soil-crop system with N and improving weed control. However, competition for resources may impair wheat performance. Relay intercropping in springtime in growing winter wheat is expected to limit competition for resources from the legume. The aim of our study was to analyze wheat performance and resource competition in relay intercropping systems with legume cover crops under various environmental conditions. Eight field experiments were conducted on organic grain-oriented farms located in southeast France. Black medic (Medicago lupulina), alfalfa (Medicago sativa), red clover (Trifolium pratense) and white clover (Trifolium repens), undersown at wheat tillering stage, were compared with a sole crop of winter wheat (Triticum aestivum cv. Lona). The aerial biomass of wheat and legumes and total N content of wheat were determined at both the flowering stage and harvest time of the wheat. The main trophic resources (water, N and light) were monitored at similar stages. Wheat grain yield and grain protein content were also measured. Sites were classified according to wheat sole crop performance at harvest to evaluate the effect of relay intercropping in the various conditions tested. In all but one of the thirty-two treatments, wheat grain yield was not significantly disturbed by relay intercropping whatever the aerial development of legumes. Abundant aerial development of legumes after flowering (>20% of the aerial biomass of wheat at harvest) was associated with a mean significant decrease in wheat grain protein content of 8.5% of the control treatment value, this occurring in one third of the situations. These ratios of aerial biomasses of legumes compared to wheat were also associated with reductions in soil moisture and wheat N uptake. The effect on the availability of trophic resources for wheat may have led to a decrease in grain protein content without having any effect on grain yield. Sites which registered a low performance for wheat sole crops were less negatively impacted by the presence and aerial development of legumes. The performance of the four legume species and the mechanisms of induced disturbance of resource availability are then discussed. Finally, we try to define ranges of legumes' development and resource availability in which wheat performance was maintained or limited. (C) 2013 Elsevier B.V. All rights reserved.

International audience; The present major agricultural issues are to feed the world and reduce negative environmental impacts. To this end, organic farming appears as a promising solution. However organic farming has several drawbacks such as difficult weed management. Indeed weeds can reduce crop yields. Therefore there is a need for improved decision support tools for weed management in organic farming. An existing weed competition model actually predicts the effect of early multispecies weed density, both on organic wheat yield loss and on the weed density at flowering stage. However main existing models do not take into account the activity of end-users, e.g. farmers, during model design. Therefore we analysed weed information acquisition by farmers using the dynamic environment theory to design a decision support system that takes into account end-users. We interviewed eight French organic farmers. We analysed interview data using a coding scheme inspired by dynamic environment theory. Our results show that weed quantity was the information most frequently collected by organic farmers both for short- and long-term crop management. This information was compatible with early weed density, the main input of the previously developed models. Findings also show that procedures for gathering information and processing depended on farmer profiles. We also show that a conceptual model based on dynamic situations and a coding structure were appropriate for taking into account the information elaborated by end-users. Finally we propose further design of a decision support system for tactical organic weed management using a participatory approach.

International audience; Organic agriculture could achieve the objectives of sustainable agriculture by banning the use of synthetic fertilizers and pesticides. However, organic crops generally show lower performances than conventional ones. In France, organic winter wheat production is characterized by low grain protein content. There is a crucial need for better understanding the variability of grain protein content, because millers require batches with values over 10.5% of dry matter. Here, a regional agronomic diagnosis was carried out to identify the limiting factors and crop management practices explaining the variability of grain protein content. The studied field network was a set of 51 organic winter wheat plots in south-eastern France. The mixed-model method was used for identifying and ranking the limiting factors and the crop management practices responsible for variation in limiting factors. Our results show that the grain protein content variation was mostly explained by the baking quality grade of the cultivar, crop nitrogen status and weed density at flowering. There was a positive correlation between grain protein content and both crop nitrogen status and weed density. To a lesser extent, climatic factors also explained grain protein content variability. A lower water stress increased grain protein content, whereas an increase in the photothermal quotient and daily temperature over 25 °C reduced grain protein content. In south-eastern France, grain protein content of organic winter wheat could be increased by improving fertilization management, using an improved baking quality grade cultivar, choosing a legume fodder crop as preceding crop, or by avoiding late sowing dates.

International audience; The development of sustainable cropping systems is a key priority for agronomists and crop scientists. A first step involves understanding the relationship between cropping system performance and farmers’ practices. To complete this step, a methodological framework entitled Regional Agronomic Diagnosis (RAD) has been developed. During the last ten years, the scope of the regional agronomic diagnosis has been enlarged to include several factors describing crop quality and the environmental impact of cropping systems. Regional agronomic diagnosis has led to several major advances such as (1) the assessment of the effect of preceding crop and soil structure on malting barley quality in France and (2) the assessment of the effects of ploughing, nematicide use and fertilisers on soil properties in intensive banana plantations in the West Indies. Improvements have also been gained in methodology, particularly by the selection of indicators for assessing the effects of crop management, soil and weather conditions, and data analysis. Finally, regional agronomic diagnosis has been integrated into more general approaches of agricultural development. We review here this methodological progress.

International audience; A diagnostic method for assessing regional variations in yield was implemented for a network of 24 organic wheat fields located in two neighboring regions, Diois and Val de Drôme (France). We studied: yield and its components; field environmental conditions of the fields; relations between indicators of potential limiting factors and yield components; and linkages between crop management and yield-limiting factors. The yield performances were low and variable (3.5 ± 1.4 t*ha-1). The relative kernel number (RKN) was significantly related to nitrogen nutrition and weed density at flowering. The nitrogen nutrition index (NNIf) had a strong and positive effect on relative kernel number, while weed density (1/WF) had a negative effect. The percentage of kernel number variation explained by the regression model (RKN = 0.112 + 0.609 × NNIf + 0.2 × 1/WF) was adequate (Adj. R2 = 0.53) with a RMSE of 0.09. The duration of the period of grain filling, reflected in the temperature sum, had a strong and positive effect on relative kernel weight (RTKW), while soil compaction and high temperature had a negative influence. Adjusted R2 for the model was 0.42 with a RMSE of 0.16. The results confirm that legumes preceding crops improve nitrogen nutrition on subsequent winter wheat, e.g. the Nitrogen Nutrition Index at flowering (NNIf) = 0.51 ± 0.12 for a crop rotation with a rate of legumes over 37% vs. 0.41 ± 0.11 for a crop rotation with a rate of legumes under 25%. Alfalfa preceding crops significantly limited the weed density at harvest while stony soils and early sowing (before November 1st) enhanced weed density.

International audience; Organic farming is increasingly recognized as a prototype for sustainable agriculture. Its guidelines ban the use of artificial fertilizers. However, organic farms may import nutrients from conventional farming through material exchanges. In this study, we aimed at estimating the magnitude of these flows through the quantification of nitrogen, phosphorus and potassium inflows from conventional farming to organic farming. Material inflows and outflows were collected for two cropping years on 63 farms. The farms were located in three French agricultural districts distributed over a gradient of farming activity defined by both the stocking rate and the ratio of the farm area under arable crops. Our results showed that on average, inflows from conventional farming were 23%, 73% and 53% for nitrogen, phosphorus and potassium, respectively. These inflows were strongly determined by the farm production systems. However, for farms similar in terms of production systems, the inflows also depended on the local context, such as the proximity of organic livestock farms: the reliance of organic farming on conventional farming was lower in mixed than in specialized districts. These results highlight the necessity to quantify the contribution of nutrient inflows from conventional farming when assessing organic farming and development scenarios.