Legume crops hold promise to diversify the currently simplified rotations that dominate Europe and to increase the sustainability of European farming systems. Nevertheless, most legumes have been ignored by farmers, advisors, and value chain agents in the EU, where legumes are estimated to occupy only ~2% of arable land. Recent surveys find that farmers see a lack of knowledge on the agroecological impacts of (re)introducing legumes as a key barrier to legume adoption. A review of current research on the agroecological potential of legume-inclusive cropping systems would help in assessing whether research targeting sufficiently supports farmers in overcoming this barrier. We have systematically reviewed and synthesized published literature reporting on agricultural ecosystem service delivery in European cropping systems with legumes included compared to those without legumes. Our analysis of 163 published articles revealed: (1) the bulk of published research addresses production-related services delivered by few legume species (pea, clover, faba bean, and vetch, 70% of reviewed studies) comparatively assessed in cereal-based rotations; (2) substantial knowledge gaps also exist, encompassing ecosystem services with less direct relevance to economic outcomes (e.g., biodiversity) and with potential for high variability (e.g., pest and disease suppression); (3) studies at plot-level and within-season scales dominate (92% and 75% of reviewed studies, respectively). Assessed in the context of recent complementary studies, we find that a limited research focus is both counter to knowledge demands from farmers and likely the result of self-reinforcing socio-technical regimes which prioritize production over non- or indirectly-marketable ecosystem services. We conclude that scientists in Europe should diversify research to include legume species, ecosystem services, contexts, and scales not yet well studied, in order to provide the agroecological knowledge base farmers need to amplify the potential benefits of crop diversity.

豆类作物有望使目前简化的主导欧洲的轮作多样化，并提高欧洲耕作制度的可持续性。但是，欧盟的农民，顾问和价值链代理商忽略了大多数豆科植物，据估计，那里的豆科植物仅占可耕地的2％。最近的调查发现，农民认为缺乏对（再）引入豆科植物作为其主要障碍的农业生态影响的知识。对目前有关豆类作物种植系统农业生态潜力的研究进行回顾，将有助于评估针对性研究是否充分支持农民克服这一障碍。我们已系统地审查和综合了有关欧洲种植系统中包括豆类的农业生态系统服务交付情况的报告，并与不含豆类的系统进行了综合报道。我们对163篇已发表文章的分析显示：（1）大部分已发表的研究针对的是少数几种豆类品种（豌豆，三叶草，蚕豆和紫,，提供了70％的综述研究）提供的与生产相关的服务，这些谷物在基于谷物的轮作中进行了比较评估; （2）还存在大量知识差距，其中包括与经济成果（例如生物多样性）的直接相关性较低，并且具有高度可变性的潜力（例如病虫害和疾病抑制）的生态系统服务；（3）在地块级和季节内规模的研究中占主导（分别为经审查的研究的92％和75％）。在最近的补充研究的背景下进行评估，我们发现有限的研究重点既与农民的知识需求背道而驰，也可能是自我强化的社会技术制度的结果，这种制度将生产优先于不可出售或间接销售的生态系统服务。我们得出的结论是，欧洲的科学家应该使研究多样化，以包括豆科植物种类，生态系统服务，背景和尚未得到充分研究的规模，以便为农民提供农业生态知识基础，以扩大作物多样性的潜在利益。