<p>This paper examines the relationship between crop diversity, organic farming, and agricultural efficiency across European regions using data from the Farm Accountancy Data Network (FADN). Technical efficiency is measured via a conditional Debreu-Farrell input-oriented index within a Data Envelopment Analysis (DEA) framework, based on labor, capital, and land inputs. Efficiency scores are analyzed using panel data models with correlated random effects to distinguish within- and between-region variation. We find a statistically significant positive effect of organic farming on efficiency within regions but not across regions, suggesting that local adoption improves productivity even if regional averages do not. In contrast, crop diversity is linked to lower efficiency within regions - a counterintuitive result that possibly reflects adaptation to external shocks rather than productivity aims. Taking into account the strong spatial dependence, we apply spatial panel models to a balanced subsample, confirming the robustness of our results. Climate variables further inform the analysis: temperature variability reduces efficiency, while higher average temperatures support it. The negative association between crop diversity and efficiency highlights the dual role of diversification as a resilience strategy and a possible productivity trade-off, which deserves further research.</p>