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National audience; En Agriculture de Conservation des Sols (ACS), la perturbation minimale du sol est l’un des trois prin-cipes. Si l’impasse se fait sentir mieux vaut repenser le système que de laisser le mur se rapprocher à grands pas. Trois types de gestion d’interculture (Labour, travail superficiel (TCS) et semis direct avec glyphosate (SD)) ont été comparés sur des parcelles conduites sans labour depuis 17 ans dont les 7 dernières années en ACS sur le domaine de l’INRA de Dijon avant implantation d’un blé, sur un dispo-sitif en bandes répétées sur quatre parcelles. Des relevés de flore adventice, rendement et compo-sante de rendement ont été faite. Les densités moyennes sont faibles pour le Labour et SD (environ 25 individus/m²). De forte hétérogénéité de densité adventice sont observées en TCS, avec des zones allant de quelques individus de vulpins des champs à plus 300 par m². L’ensemble des modalités pré-sentent du vulpin et du gaillet. Leurs densités sont très faibles en Labour comparées au SD et TCS. On observe six fois moins de vulpin en Labour (4 plantes/m² en moyenne) qu’en SD (21,4/m²) ou en TCS (24,5/m²). On observe 2 fois moins de gaillet en labour (2,5/m²) qu’en SD (4,7/m²) ou en TCS (4,9/m²). Le type de travail du sol mis en oeuvre a été à l’origine de changement drastique de flore (richesse, composition), malgré une conduite homogène durant 17 ans. Statistiquement, il n’y a pas eu de diffé-rences de rendement entre les modalités, même si la modalité SD produit 5 q/ha de moins que les modalités TCS et Labour. Aucune différence en termes de composantes de rendement n’est observée. Can tillage overcome a weed management deadend in conservation agriculture? A com-parison of tillage options Minimal soil disturbance is one of the fundamental pillars of conservation agriculture (CA). In case of weed management difficulties, reintegrating tillage in the system might be the most viable option. Three types of fallow management (ploughing (CT), superficial tillage (RT), no-till with glyphosate (NT)) were compared on four fields after 10 years of no-plough and 7 years of no-till at the INRA experi-mental farm in Epoisses. Weed density, crop productivity and yield components were assessed in the following winter wheat. Blackgrass and cleavers were the two most problematic species of the exper-iment. Weed density was low in CT and NT (~25 pl/m²) while highly variable weed densities were ob-served in RT, with densities of blackgrass varying from a few to 300 plants/m². Blackgrass density was six times lower in CT (4 pl/m²) than in NT or RT (21-25 pl/m²). Cleavers density was half as important in CT (2.5 pl/m²) than in NT or RT (~5 pl/m²). The reintegration of tillage after 17 years of CA proved be a major driver of weed communities (density and richness). No significant differences were observed in terms of yield or yield components, even if grain yield was 0.5 T/ha lower in NT than CT or RT.

Coffee is a key export commodity of East Africa, but average smallholders' yields are low. To guide sustainable yield improvements of smallholders' coffee systems, we investigated coffee yield components in three different types of coffee cropping systems along an altitude gradient (1100−2100 m.a.s.l.) during two production years (2015 and 2016). We selected 810 coffee trees distributed over 27 farms and monitored number of stems per tree, fruit load per branch, productive nodes per branch (on four branches of one stem per tree) and number of productive branches per stem (on one stem per selected tree) in both years. Additionally, we monitored productive stems per ha, coffee tree density and cherry weight in combination with pest and disease occurrence and management information from interviews. Coffee farms were classified as Coffee-Open (CO) (< 20 % shade cover), Coffee-Banana (CB) (coffee dominantly intercropped with bananas) or Coffee-shade Tree (CT) (coffee dominantly intercropped with shade trees). Coffee-Banana had larger yield per ha (green bean kg ha−1) (1086±736 kg ha−1) and yield per stem (green bean kg stem−1) (0.24±0.16 kg stem−1) than CO (670±457 kg ha−1 and 0.21±0.26 kg stem−1) and CT (428±259 kg ha-1 and 0.10±0.12 kg stem−1). Fruit loads, productive nodes, productive branches and cherry weight declined with shade cover, especially for shade cover>30 %. Additionally, the same yield components correlated negatively with number of stems per tree. Fertilizer and fungicide use were related to more productive branches and cherry weight respectively, and stem borer was identified as the most important pest in this area. Our results suggest that yield in the region could be increased, i) by maintaining shade at an intermediate level, particularly at low and mid altitude and by reducing the number of stems per coffee tree (< 4), and ii) by improving soil fertility and protection against pest and disease.