WP5 of the ENFASYS project is designed to test the effectiveness of co-created systemic and behavioural interventions through experimental research (T5.1; T5.2; T5.3) and system dynamic modelling (T5.4). The goal is to evaluate how these interventions perform in real-life contexts, assessing their capacity to foster sustainable farming system transitions at both the case-study level and broader national levels. Task 5.1 contributes to this objective by focusing on behavioural interventions and testing the impact of tailored nudging strategies on farmers’ behavioural determinants across a diverse set of farming contexts. This deliverable reports on the design, implementation, and evaluation of nudging interventions developed through close collaboration with the case study coordinators. Each intervention was tailored to a specific sustainability challenge and target behaviour, aiming to improve the behavioural drivers of sustainable farming. A total of 9 case studies across 8 countries have been included in the experimental phase of Task 5.1. For each of them, a validated nudge intervention has been developed and its effects assessed using a quasi-experimental approach. All interventions were evaluated adopting a quasi-experimental Difference-in-Differences (DiD) approach (Angrist & Pischke, 2009), comparing behavioural indicators between a control and a treatment group over time. This design was chosen for both ethical and practical reasons, including difficulties in random assignment and the need to ensure feasibility in agricultural contexts. The nudge interventions were implemented through a structured pre/post-survey design based on their influence on a set of psychological and behavioural variables derived from the Theory of Planned Behaviour (Ajzen, 1991), Self-Determination Theory (Deci & Ryan, 1985), the MINDSPACE framework (Dolan et al., 2010) and the RESET model (Lam et al., 2017). The nudge interventions addressed a variety of behavioural domains, such as the adoption of agri-environmental and climate measures (AECMs), regenerative and biodiversity-friendly practices such as reduction of pesticide use, and participation in direct selling (Palm-Forster et al., 2020; Davidson 2021). All the nudges combined informational and social norm-based elements, tailored to context-specific barriers and motivations identified through scoping reviews and stakeholder engagement. Each case study developed and tested its nudge message, translated into local languages and disseminated in visually engaging formats. Following the implementation, data were analysed to measure the impact of the intervention on a wide set of behavioural antecedents, such as perceived behavioural control, social norms, behavioural intentions, attitudes, and self-efficacy. A synthesis of preliminary aggregated results showed a multifaceted impact of the nudging interventions across case studies, highlighting the necessity to tailor behavioural interventions and the practices to be promoted to the characteristics of the target contexts and populations, with a particular focus on the perceived feasibility and familiarity of proposed sustainable practices.