Low-Input maize-based cropping systems implementing IWM match conventional maize monoculture productivity and weed control

Conventional Maize Monoculture (MM), a dominant cropping system in south-western France, is now questioned for environmental reasons (nitrate leaching, pesticide use and excessive irrigation). Three low-input Cropping Systems (CS) using diverse weeding strategies (MMLI, a low-input MM implementing ploughing, a combination of on-row spraying and in-between row cultivation and cover crops; MMCT, conservation tillage MM implementing chemical control and cover crops; Maize-MSW, maize managed similar to MMLI but rotated with soybean & wheat) were compared to a reference system (MMConv, a conventional MM with tillage and a high quantity of inputs). Potential of Infestation of weeds (PI), weed biomass and crop production of these CS were compared during the first five years after their establishment. fields were also assessed in weed-free zones hand-weeded weekly in 2014 and 2015. Weed communities did not drastically differ among CS. PI and weed biomass were higher in MMCT, especially for Echinochloa crus-galli (L.) P.Beauv. and were comparable between MMConv, MMLI and Maize-MSW. Analysis of covariance between CS and weed biomass did not reveal a significant interaction, suggesting that weed biomass affected yield similarly among the CS. Comparison between weedy and weed-free zones suggested that weeds present at maize maturity negatively affected yields to the same extent for all four CS, despite having different weed biomasses. Grain yields in MMConv (11.3 ± 1.1 t ha−1) and MMLI (10.6 ± 2.3 t ha−1) were similar and higher than in MMCT (8.2 ± 1.9 t ha−1. Similar yields, weed biomasses and PI suggest that MMLI and Maize-MSW are interesting alternatives to conventional MM in terms of weed control and maize productivity and should be transferred to farmers to test their feasibility under wider, farm-scale conditions

Vulpia myuros, an increasing threat for agriculture

Vulpia myuros is an annual grass species of Mediterranean origin, which has achieved a global distribution. It is a fast-growing species, with high colonisation and competitive abilities. This species is considered an invasive weed in most countries where it has been introduced, with highly negative economic impact where it now dominates. It is increasingly found to be a problematic weed in winter cereals, especially in no-till and reduced tillage systems, across Europe, United States and Australia. Seeds of V. myuros have reduced germination potential when buried. However, where tillage interventions are reduced, ideal conditions for V. myuros are created. Minimum and no tillage practices are increasing worldwide, with a concomitant increase in the spread and abundance of V. myuros. Effectiveness of herbicides is mostly suboptimal, in particular for well-established populations forming dense swards, even though no herbicide resistance has yet been identified. An integrated management approach, increasing crop diversification combined with management adaptations, possibly including herbicides is suggested as an effective control strategy. Despite increasing research on V. myuros, more information is needed to optimise the management of this weed. Based on the species’ Mediterranean origins and adaptation to warm and dry environments, an increase of its global importance may be expected with climate changes. It is thus paramount to increase the awareness around this species, improve its identification in the field, and monitor its spread before it becomes a concern of similar magnitude to grass weeds like Alopecurus myosuroides or Lolium rigidum

Editorial: Integrated weed management for reduced weed infestations in sustainable cropping systems

International audienceWeeds are a major biotic constraint of agricultural systems worldwide interfering with crop production and resource use efficiency (Oerke, 2006; Colbach et al., 2020). Chemical control is a cost-and time-effective weed management method and for that reason remains as the most widely and frequently used method to sustain agricultural productivity and food security in the current era. However, repeated use of a limited number of herbicide active ingredients in non-diversified crop rotations enhances the selection of herbicide-resistant weed biotypes. The over-reliance on chemical weed control has led to shifts in weed communities (Mahaut et al., 2019) which are now becoming dominated by highly competitive and herbicide-resistant prone species able to cause significant yield losses (Adeux et al., 2019b). Widespread herbicide resistance (Heap, 2023) accompanied by the increasing concern of herbicides entering the food chain and/or impacting the environment has created a tremendous demand for alternative weed management methods. Alternative weed management practices that reduce weed populations indirectly lowers selection pressure thus helping delay the evolution of further herbicide resistance. Controlling weeds during the critical period of weed removal is paramount for achieving the full yield potential of any crop (Zimdahl, 1988; Colbach et al., 2020). In conservation tillage with cover cropping, research on the critical period of weed removal is warranted to further elucidate cover crop weed suppressive attributes and efficient utilization of herbicides (Kumari et al.). Preventive weed control measures include all the possible means that restrict the entry and establishment of weeds in an area. Cultural control is an ecological method of weed control in which good crop management methods are followed to stimulate rapid crop growth and canopy closure (Petit et al., 2018). Cultivar selection, Frontiers in Agronomy frontiersin.org 0

Field margin grass strips: opportunity or threat for the weed management in arable landscapes?

Prod 2017-295 EA GESTAD INRAInternational audienceSown grass strips could be an opportunity (refuge) or a threat (source of crop infestation) for weed management in arable landscapes. Firstly, our field surveys recorded 187 weed species, among which 90% were arable species, mostly perennial and wind dispersing species, here mostly represented by the Asteraceae family. Even if sown grass strips harboured a high richness of unsown species (26 weed species/grass strip), the richness did not vary according to the time since establishment. Weed community composition drastically changed over time, with a quick shift (within the 2 first years) from annual to perennial species, and from common agricultural weeds to non-arable species. Secondly, flora surveys performed with continuous transects from the field margin to the field centre showed clear plant spatial patterns. The sown grass strips acted as an ecotone with a sharp vegetation transition. Weeds occurring within the centre of the sown grass strips radically differed from species occurring within the first 0.5m of the cultivated area (only 15% of similarity between communities occuring in both habitats). Moreover, classical field margins influenced the weed composition up to 4.5m in the field whereas sown grass strips influenced the weed composition only up to 2m. We concluded that sown grass strips could be an opportunity to maintain plant diversity at the landscape scale and to decrease weed dispersion from the field margin to the field core in the short term. However, we discussed the long term impacts, especially to maintaining high level of annual species and segetal species in these perennial semi-natural habitats

Nuisibilité des adventices : définitions, méthodes de quantification, et regard critique sur les connaissances actuelles

National audienc

Benefits of a more functionally diverse weed flora and opportunities/barriers to manipulating weed diversity through integrated weed management - KEYNOTE

International audienc

Effet des couverts et du non travail du sol sur la flore adventice : les empêcher de lever puis les concurrencer

National audienc

Flore adventice en agriculture de conservation des sols ou en système en transition : diversité des communautés et gestion

National audienceAprès avoir rappelé ce qu’est la diversité taxonomique, biologique et fonctionnelle de la floreadventice, l’exposé montrera ce que change la mise en œuvre de l’ACS du point de vue de laflore adventice et du désherbage. L’orateur s’interrogera sur ce qu’est la gestionagroécologique de la flore adventice, en quoi l’ACS peut être un moteur et comment adapterles pratiques. Le risque de résistances aux herbicides, les effets du changement climatique etles leviers à mettre en œuvre dans la cadre d’une approche systémique seront considéré