Below ground microbial diversity as influenced by coffee agroforestry systems in the Western Ghats, India

Soil microorganisms viz. bacteria, fungi, actinomycetes and arbuscular mycorrhizal (AM) fungi present in different typologies of coffee production systems were compared. In this study, two types of coffee plants, namely Arabica and Robusta, were grown under different agroforestry management such as coffee under one specialized shade species, multi-story coffee systems with 2 shade tree species, and coffee with 3 or more tree species under moist deciduous and evergreen ecological conditions. Samples were collected from 36 points to include different coffee ecosystems. The highest number of infective propagules of AM fungi was encountered in Arabica coffee under evergreen conditions. Population of bacteria, fungi and actinomycetes were higher under evergreen ecosystem compared to that of deciduous conditions. The population of nitrogen fixing bacteria was more than double in evergreen conditions compared to deciduous ecosystem. Number of lignin decomposing bacteria was higher in evergreen compared to deciduous conditions, but starch hydrolyzing bacteria and pectin-utilizing bacteria were more in deciduous ecosystem. Actinomycetes DAT2-1 isolated from deciduous ecosystem showed antagonistic activity against the root pathogen Fusarium chlamydosporum. It can be concluded that evergreen coffee system supports higher population of microorganisms. Of the two species of coffee, Arabica harboured more AM fungi, bacterial population, N fixers, P solubilizers and cellulose decomposing organisms while Robusta harboured higher number of fungi and actinomycetes. Of the three typologies, coffee grown under two shade tree species supported higher population of all microorganisms.