In this paper, we analyse the effects of different types of formal collaboration and research topics on research impact of academic articles in the area of agricultural, resource, environmental, and ecological economics. The research impact is measured by the number of times an article has been cited each year since publication. The topics within the area of research are modelled using latent semantic analysis. We distinguish between the effect of institutional, national, and international collaboration. We use statistical models for count data and control for the impacts of journals, publication year, and years since publication. We find that, holding other factors constant, collaboration in the form of co-authorship increases research impact. The effect of inter-institutional collaboration within same country is similar to the effect of collaboration within same institution. However, international collaboration results in additional increase in impact. We find that the topic of a paper substantially influences number of citations and identified which topics are associated with greater impact. The effects of different types of collaboration on citations also vary across topics.