Influence of farm diversity on nitrogen and greenhouse gas emission sources from key European dairy cattle systems: A step towards emission mitigation and nutrient circularity

CONTEXT: European dairy cattle production systems (DPS) are facing multiple challenges that threaten their social, economic, and environmental sustainability. In this context, it is crucial to implement options to promote the reconnection between crop and livestock systems as a way to reduce emissions and enhance nutrient circularity. However, given the sector's diversity, the successful implementation of these options lacks an evaluation framework that jointly considers the climatic conditions, farm characteristics, manure management and mineral fertilisation practices of DPS across Europe. OBJECTIVE: This study aims to develop a modelling and statistical framework to assess the effect of climatic conditions, farm characteristics, manure management and mineral fertilisation practices on the on-farm sources of greenhouse gas (GHG) emissions and nitrogen (N) losses from ten contrasting case studies for dairy production across Europe, identifying options for emissions mitigation and nutrient circularity. METHODS: Using the SIMSDAIRY deterministic whole-farm modelling approach, we estimated the GHG emissions and N losses from the ten case studies. SIMSDAIRY captures the effect of different farm management choices and site-specific conditions on nutrient cycling and emissions from different components of a dairy farm. In addition, we applied the Factor Analysis for Mixed Data multivariate statistical approach to quantitative and qualitative variables and identified relationships among emissions, nutrient losses, and the particular characteristics of the case studies assessed. RESULTS AND CONCLUSIONS: The results showed how intensive case study farms in temperate climates were associated with lower enteric emissions but higher emissions from manure management (e.g. housing). In contrast, semi-extensive case study farms in cooler climates exhibited higher N losses and GHG emissions, directly linked to increased mineral fertilisation, excreta during grazing, and slurry application using broadcast. Furthermore, the results indicated opportunities to improve nutrient circularity and crop-livestock integration by including high-quality forages instead of concentrates and substituting mineral fertilisers with organic fertilisers. SIGNIFICANCE: The presented framework provides valuable insights for designing, implementing, and monitoring context-specific emission mitigation options and nutrient circularity practices. By combining whole-farm modelling approaches and multivariate statistical methods, we enhance the understanding of the interactions between sources of N losses and GHG emissions. We expect our findings to inform the adoption of emissions reduction and circularity practices by fostering the recoupling between crop and livestock systems.