Recently adopted in France, conservation agriculture still faces some challenges to its adoption, particularly weed management. To highlight the weed management practices used by farmers in conservation agriculture and the changes induced by its adoption, a large sample of 425 French farmers were invited to complete an online survey. Weed management practices used by farmers were requested for three periods: before adoption, during the first years of conservation agriculture (one to two years after adoption), and when the agricultural system is considered “mastered” by the farmer. The use of each farming practice was firstly studied independently for each period. Then, a multiple correspondence analysis followed by a hierarchical ascendant classification resulted in groups of farmers with different combinations of practices for each period. Finally, the groups of farmers were followed through the periods. Results showed that changes in weed management done according to farmers when adopting and mastering conservation agriculture are multiple and vary according to farmers and their previous weed management. Although some similar choices were identified, some farmers’ trajectories, especially those with a prior combination driven by either a soil disturbance strategy or a crop competitiveness strategy, are difficult to identify when adopting conservation agriculture. Upon mastering the agricultural system, farmers’ choices become more apparent.
Le semis direct sous couvert repose sur l’application simultanée et continue de trois principes : la réduction quasi-totale du travail du sol, une couverture organique des sols et une rotation diversifiée. Ce système agricole adopté en France à partir des années 2000 sous l’impulsion de groupes d’agriculteurs est en extension. Pour les agriculteurs, adopter un nouveau système agricole revient à modifier, de manière plus ou moins importante, leurs pratiques. Concernant le semis direct sous couvert végétal, peu d’informations existent. Cet article a pour objectif d’éclairer les modifications que peut induire sa mise en place. Pour cela, il s’appuie sur les réponses de 425 agriculteurs français à une enquête en ligne. Pour 30 % des agriculteurs, le semis direct sous couvert constitue une modification complète du système agricole. La réduction quasi-totale du travail du sol est le principe qui entraîne le plus de modifications (pour 96 % des agriculteurs). Au contraire, la diversification de la rotation connaît le moins de modifications (48 % des agriculteurs). L’absence d’une modification de la rotation peut s’expliquer par une rotation déjà diversifiée en place ou l’incapacité pour les agriculteurs d’ajouter de nouvelles cultures à leur rotation. L’optimisation de la couverture végétale du sol entraîne une modification des pratiques pour 67 % des agriculteurs. Durant les premières années, les agriculteurs s’orientent majoritairement vers l’utilisation de couverts temporaires plurispécifiques. Bouleversant certains fondamentaux de l’agriculture, ces agriculteurs minimisent les risques encourus en favorisant une transition progressive et en partageant les connaissances acquises.
Agroecological farming uses crop and non‐crop plant biodiversity to promote beneficial insects supplying pollination and biocontrol services to crops. Non‐crop plants (sown or weeds) are integral to supporting these beneficial insect species interactions. How the uplift of biotic complexity by agroecological management (crop diversification, ecological infrastructure) influences mutualistic and antagonistic insect interactions regulating the reproduction of non‐crop plants remains less understood. Using a pesticide‐free farm‐scale (125 ha) agroecological experiment, we tested how the individual reproduction of pollinator‐dependent, non‐crop plant species with different flowering phenology (Cyanus segetum, Centaurea jacea) and their mutualistic (pollinator) and antagonistic (seed herbivore–parasitoid) insect interactions were affected by agroecological practices. Seed set and species interactions of replicate C. segetum and C. jacea randomly introduced to field margins were correlated with floral resource heterogeneity at focal plant (e.g. flower display size), local community (floral richness/abundance driven by sown wildflower or grass margins) and local landscape (crop diversification, area of semi‐natural habitat or mass flowering crops) scales. At the seasonal peak of non‐crop floral diversity and abundance, antagonistic interactions weakly regulated C. segetum seed set with gains from pollinator activity predominating. Conversely, C. jacea, which flowered past the peak of non‐crop floral diversity/abundance, benefited from the promotion of seed herbivore parasitism and pollinator activity by the local landscape cover of semi‐natural habitat and mass flowering crops. Synthesis and applications. Agroecological management produced spatial and temporal gradients in crop and non‐crop floral resources that interacted to modify pollinator or seed herbivore–parasitoid interactions and Cyanus segetum and Centaurea jacea seed set. The degree of phenological overlap between C. segetum and C. jacea flowering and floral resources in the local community or landscape dictated the type and level of exposure to insect interactions influencing reproduction. Design of agroecological practices to deliver pollination and biocontrol services must consider how effects will vary with species traits and the mutualistic (pollination) and antagonistic (herbivory, parasitism) interactions governing non‐crop plant reproduction. Agroecological management supporting beneficial insect interactions may feedback to help restore functional non‐crop plant populations and associated biodiversity, potentially reducing the frequency of management interventions (e.g. re‐sowing wildflower strips).
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