Addressing the negative externalities of conventional, high-input agriculture requires identifying alternative systems that encompass all dimensions of sustainability. Agroecology, through ecological intensification and a diverse suite of multi-scale practices, has the potential to meet this challenge. However, knowledge on the long-term technical feasibility and performances of agroecological cropping systems remains limited, particularly for pesticide-free cropping systems spanning a tillage intensity gradient. Eight experimental pesticide-free cropping systems were evaluated across two sites and 70 fields over four years using 14 indicators covering productivity, economic, environmental, and social outcomes. These systems were compared with 25 conventional and organic reference systems in their vicinity, using a linear mixed model fitted for each indicator. A redundancy analysis (RDA) was carried out to examine the relationships between farming practices and performance profiles and quantify the relative importance of each practice. Overall, experimental pesticide-free systems showed lower productivity and profitability, as reductions in input costs were insufficient to offset yield declines and higher equipment expenses. Some systems achieved substantial reductions in energy use and greenhouse gas emissions, largely due to decreased nitrogen fertilization and diversified crop rotation, including crops that require less nitrogen, such as legumes. Performance varied with tillage intensity: conventional tillage outperformed reduced- and no-tillage systems, which were strongly constrained by weed pressure. The findings highlight the complexity of managing agroecological pesticide-free systems and reveal key technical lock-ins. The study also identifies opportunities to improve system performance through crop diversification, legume integration, tillage management, and crop-livestock integration. By quantifying trade-offs among yield, profitability, and environmental outcomes, this work provides critical insights for the design and adoption of sustainable agroecological cropping systems.

To reduce reliance on herbicides and maintain crop productivity, integrated weed management (IWM) seeks to optimize synergies between diverse sets of weed management practices combined at the cropping system scale. Nevertheless, data on weed community response to the long-term implementation of IWM practices remain scare. Here, we assessed the effects of four IWM systems with contrasting objectives and practices (S2: transition from superficial tillage to conservation agriculture; S3: no-mechanical weeding; S4: mixed mechanical and chemical weeding; S5: herbicide-free; all with 6 year rotations) compared to a conventional reference (S1: herbicide-based with systematic plowing and a 3 year rotation) on taxonomic and functional weed community composition and structure after 17 years of continuous implementation. We examined the legacy effects of these systems with a uniformity trial consisting of winter wheat managed uniformly across the systems as well as with a novel in situ weed seedbank approach involving tilled strips. We found that resulting weed communities in IWM systems were more species rich (species richness from 1.1 to 2.6 times greater) and more abundant (total density from 3.3 to 25 times greater) than those observed in the reference system, and differed in term of taxonomic and functional composition. In addition, we found that, when systems shared the same weed species, germination patterns of two thirds of the species differed between systems, highlighting the selection pressures some IWM practices exert on weeds. We showed that analyzing the superficial germinable seedbank in situ with tilled strips could provide a comprehensive view of resulting weed communities and be helpful in developing cropping systems that foster agroecological weed management.

Cropping system (CS) diversification appears as a promising solution to increase CS sustainability. However, weed community response to different options of CS diversification remains poorly documented. Moreover, these effects are expected to be more pronounced in experimental than commercial farms because experimental farms explore more diverse combinations of farming practices. We hypothesized that (i) CS diversification would increase weed diversity at multiple spatio-temporal scales but that (ii) different options of CS diversification would select different weed communities and that (iii) responses could differ between experimental and commercial farms. Hence, weed density per species was measured over a 6-year time period in a CS experiment and in a farmers’ network (both resorting to diverse CSs that were numerically summarized to allow their comparison, i.e. different positions along gradients of tillage intensity, herbicide use, crop rotation length etc.). Weed density measures were used to compute weed diversity indices (taxonomic and functional, at annual and plurennial scales) and community weighted means on key response traits for each CS. All experimented alternative CSs (diversified crop sequences with coherent but different combinations of weed management tools) showed that diverse combinations of agronomic tools are available to increase weed diversity, as highlighted by a 3 and 2-fold increase in species richness at the annual and plurennial scales, respectively. In contrast, only one farmer CS (3-year rotation, low tillage intensity, intermediate herbicide reliance) showed significantly higher levels of weed diversity, possibly because the reduced tillage intensity was not compensated by other agronomic levers (e.g. increase of herbicide use and/or crop rotation diversity). Such outcomes were attributed to (i) reduced CS complexity in commercial compared to experimental farms and (ii) high herbicide reliance in commercial farms, irrespectively of CS complexity. Across both experimental and commercial farms, tillage, weed management and crop type appeared as the main factors structuring weed communities. Systems with reduced tillage were associated with a higher percentage of grasses and perennials. Systems with spring/summer crops and/or mechanical weeding were associated with a higher proportion of spring/summer and perennial species. These results suggest that solutions are readily available for farmers to implement sustainable weed management, but supports are required to address the factors hindering the adoption of these experimented CS in commercial conditions.

Integrated weed management encourages long-term planning and targeted use of cultural strategies coherently combined at the cropping system scale. The transition towards such systems is challenged by a belief of lower productivity and higher weed pressure. Here, we hypothesize that diversifying the crop sequence and its associated weed management tools allow long-term agronomic sustainability (low herbicide use, efficient weed control, and high productivity). Four 6-year rotations with different constraints (S2: transition from reduced tillage to no-till, chemical weeding; S3: chemical weeding; S4: typical integrated weed management system; S5: mechanical weeding) were compared to a reference (S1: 3-year rotation, systematic ploughing, chemical weeding) in terms of herbicide use, weed management, and productivity over the 2000–2017 period. Weed density was measured before and after weeding. Crop and weed biomass were sampled at crop flowering. Compared to S1, herbicide use was reduced by 46, 65, and 99% in S3, S4, and S5 respectively. Herbicide use in S2 was maintained at the same level as S1 (− 9%), due to increased weed pressure and dependence to glyphosate for weed control during the fallow period of the no-till phase. Weed biomass was low across all cropping systems (0 to 5 g of dry matter m −2 ) but weed dynamics were stable over the 17 years in S1 and S4 only. Compared to S1, productivity at the cropping system scale was reduced by 22% in S2 and by 33% in S3. These differences were mainly attributed to a higher proportion of crops with low intrinsic productivity in S2 and S3. Through S4’s multiperformance, we show for the first time that low herbicide use, long-term weed management, and high crop productivity can be reconciled in grain-based cropping systems provided that a diversified crop rotation integrating a diverse suite of tactics (herbicides included) is implemented.

19 prototypes de systemes de culture ont ete testes sur quatre sites contrastes (Picardie, Bourgogne et deux sites dans la region de Toulouse). Ces systemes de grandes cultures ont ete concus selon les principes de Protection Integree pour limiter l'usage des pesticides en general et des herbicides en particulier. Les combinaisons de leviers alternatifs ont permis de gerer durablement la flore adventice avec peu d'herbicides, et de baisser l'usage de l'ensemble des pesticides. Certains systemes permettent de concilier faible IFT et bonne performance economique. Trois sites ont ete instrumentes pour collecter des eaux de drainage et mesurer les transferts de substances actives. Ces dispositifs ont permis d'etablir un lien entre les IFT cumules et les quantites de substance transferees dans les eaux, a l'echelle d'un site et sur trois annees de mesure, confirmant ainsi le lien entre l'usage de pesticides et leur impact. Les prototypes fondes sur le semis direct ont ete decevants : ils ont necessite beaucoup d'herbicides pour maitriser les adventices, les quantites de substances actives transferees sous ces parcelles ont ete importantes, et les performances economiques ont ete moyennes.

Integrated Pest Management (IPM) aims to promote physical and biological regulation strategies that help farmers contain populations of pests (pathogens, animal pests and weeds) and to finally reduce the reliance on pesticides. It is based on the holistic combination of multiple management measures rather than on the sum of single methods, each of them having only small effects on pests reduction. Thus, to analyse the interactions between IPM measures and to evaluate the sustainability of their implementation, we require an approach considering the whole cropping system (CS), i.e. a functional entity whose complexity is more than the sum of its parts. A network of European experiments at the CS level was set up recently, and aimed at sharing data and expertise to enhance knowledge of IPM. Comparison of existing methodologies highlighted a diversity of CS designs and experimental layouts. We deduced that the concept of CS itself was viewed differently among scientists, and this affected experimental protocols. Other differences were related to the research context and objectives. Some experiments aimed to explore very innovative strategies and generated knowledge on both their effects on the agroecosystem and their ability to satisfy a set of performance targets, while others aimed to provide quickly adoptable solutions for local farmers in line with the current socio-economic constraints. In some research programmes, the experiment was part of the CS design process - and tested CS were regularly revised based on an continuous improvement loop - while in other cases CS were kept stable across years so as to enable the evaluation of their long-term cumulative effects. A critical aspect contributing to the diversity among CS experiments was the distinction between a factorial design of experimental CS and systemic approaches: factorial experiments allowed quantification of the effects of each IPM component regardless of the consistency between components defining the CS. In contrast, systemic approaches focused on the overall evaluation of CS designed with consideration of their consistency, hence maximising their ability to meet the objectives. Because CS experiments represent a huge investment in terms of economics and time, preliminary reflections of the relevance of the experimental strategy is of critical importance. (C) 2016 Elsevier B.V. All rights reserved.

Weed dynamics models are needed to test prospective cropping systems but are rarely evaluated with independent data (“validated”). Here, we evaluated the FlorSys model which quantifies the effects of cropping systems and pedoclimate on multispecific weed dynamics with a daily time step. We adapted existing validation methodologies and uncertainty analyses to account for multi-specific, multi-annual and diverse outputs, focusing on missing input data, incomplete and imprecise weed time series. Field data ranged from entirely monitored cropping system trials to annual snapshots recorded on farm fields by the French Biovigilance-Flore network. FlorSys satisfactorily predicted weed seed bank, plant densities and crop yields, at daily and multi-annual scales, at well monitored sites. It overestimated plant biomass and underestimated total flora density. Missing processes (photoperiod dependency in flowering, crop:weed competition for nitrogen) and inadequately predicted scenarios (weed dynamics in untilled fields, floras with summer-emerging species) were identified. Guidelines for model use were proposed.

INRA-AgroParisTech, UMR Environnement et Grandes Cultures, Thiverval-Grignon Université de Toulouse Ecole d’Ingénieurs de Purpan, UMR AGIR, Toulouse INRA, Unité Expérimentale ‘Grandes Cultures’ de Toulouse-Auzeville INRA, Unité Expérimentale de Dijon-Epoisses INRA, Unité Expérimentale ‘Grandes Cultures Innovation Environnement-Picardie’, EstréesMons AgroSup Dijon, UMR AgroEcologie, Dijon Agro-Transfert Ressources et Territoires (AGT-RT), Mons-en-Chaussée INRA, INRA, Unité Expérimentale ‘Grandes Cultures’, Versailles-Grignon INRA, UMR AGIR, Toulouse INRA, UR PESSAC, Versailles INRA-AgroParisTech, UMR Agronomie, Thiverval-Grignon INRA, UMR AgroEcologie, Dijon Corresponding author : benoit@grignon.inra.fr