Understanding the factors associated with adoption of ecological farming practices is a well-established topic of interest to agricultural economists. As the transition to more sustainable agriculture has become a policy priority for the European Union, broad and balanced reviews of this literature are important. We develop a systematic map of quantitative observational studies which describes the ecological practice(s) adopted, the frequency of inclusion and significance of a range of independent variables, and how the dependent variable is measured. We also conduct a quality assessment. We find that while socio-demographic variables and farm structural variables are frequently included, they were insignificant more often than they were significant. For behavioural factors we find stronger evidence for the importance of cognitive or attitudinal variables compared to dispositional attitudinal variables. We also find a growing interest in social factors which will be valuable for researchers to explore further and reflect on the policy implications of our findings.