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Abstract

Understanding the effects of different agricultural practices on arbuscular mycorrhizal fungi (AMF) communities is important for sustainable agricultural production, since AMF play an essential role in maintaining and promoting the health of crop-plant communities. Previous studies have demonstrated that organic farming methods promote greater diversity of AMF in crops like cereal and maize, and have begun to investigate the relationship between compost and AMF in coffee crops. However, research on AMF abundance in agricultural systems in the tropics is generally lacking, especially with respect to the impact on AMF abundance of conventional farming methods – that use synthetic agrochemicals, like pesticides and fertilizers – and of organic farming methods – that do not use synthetic agrochemicals, but may use organic pesticides and fertilizers. My study investigated the AMF abundance in an organic versus a conventional coffee plot in a tropical cloud forest area in Costa Rica and compared these results to AMF abundance in a secondary forest (regrown after complete or partial clearance due to human activities) as a natural system. Soil samples containing roots collected from each site were analyzed microscopically, and mean AMF root percent colonization (proportion of each root that appeared to contain AMF) was determined for each site. AMF abundance was significantly greater in the secondary forest and the organic coffee plot when compared to the conventional coffee plot. AMF abundance did not differ significantly between the secondary forest and the organic coffee plot. These results show that different agricultural practices impact AMF communities, and highlight that organic farming supports an abundance of AMF similar to that found in natural ecosystems. In particular, my study demonstrates the ability of organic farming to sustain more AMF compared to conventional farming, and the potential benefits of this increased abundance for sustainable agriculture