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RESEARCH PRODUCT

ENGAGED: System design of direct seedings under permanent cover crop without glyphosate

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Direct seeding under permanent cover crop (SDCV) corresponds to sow a crop in a multiyear vegetal cover crop(often clover) without soil perturbation. It is an emblematic technique of Conservation Agriculture whose agronomicand environmental interests are multiple because of the special attention paid to soils. However, the issue of weedcontrol and permanent cover crop control is central to SDCV culture systems. The use of non-selective herbicide suchas glyphosate is the most common technical lever for weed and cover crop management. Glyphosate is in the hotseat since the President of France announced its banning from 2023. It becomes necessary to find alternatives for thesustainability of these systems.The CASDAR Project “ENGAGED” (2018-2022) aims to build glyphosate-free SDCV growing systems with low herbicide use. The ENGAGED Project is based on three main actions:• Tracking farmers innovations• To monitor the development dynamics of weed species on plots of farmers testing conducted in SDCVwithout glyphosate.• Constructing crop system prototypes through co-design workshops with farmers from different groups,particularly Economic and Environmental Interest Groups (EEIGs).The progress of the project allows us today to identify the tracks worked by farmers and evaluate their feasibility.The field-tested strategies on the farm plots integrate all the components of the technical itinerary (sowing density,fertilization, herbicide). The results presented come from data collected over two years (2018-2019 and 2019-2020) ina network of plots located in the northwest of France. The first year was designed in order to test chemical alternativesto glyphosate without restriction on quantity of the other herbicides. The efficiency of a spring mulching, an electricweeding before the sowing, a more intense fertilization and a double sowing density were evaluated the second yearof the experiment. The observations made tend to show that the electric weeding is effective in controlling the weedflora, but has too little effect on legume cover. Furthermore, the double sowing density seems to compensate the lossof plant observed on the glyphosate-free plots, where the cover was poorly regulated, but the results are not conclusive enough to conclude to an effect of the mulching of the cover and of the intensified fertilization. A third testing year