Relative to rainforests and grasslands, banana and sugarcane soils have half the microbial biomass and highly distinct bacterial and fungal communities

Soil microbial communities mediate a range of ecosystem services and are impacted by land use. The Wet Tropics region of north Queensland, Australia, is a biodiversity hotspot with some of the world's oldest rainforests, but also has large areas converted for agriculture. We explored soil abiotic and biotic characteristics in 86 sites across four of the key land uses in this area: banana production, sugarcane production, grassland, and rainforest. Furthermore, we characterised sites where wild bananas were found in rainforests to bridge the associations found in natural and agricultural areas. Soil abiotic and biotic characteristics were found to differ between landuses, with commercial banana soils being the most distinct. Commercial banana and sugarcane soils had less soil carbon, and banana soils were also less acidic and had higher zinc and nitrate levels than other landuses. Interestingly, banana and sugarcane soils had half the microbial biomass of other landuses, including wild banana. The diversity of soil bacterial and fungal communities was also highly distinct in commercial banana soils, with significantly larger relative abundances of Fusarium oxysporum, a fungal species complex that includes important plant pathogens. Differences in soil biotic characteristics between landuses were significantly correlated with soil carbon, nitrogen, phosphorus, and pH. Our results demonstrate that land management can profoundly impact soil microbial communities, with potential consequences for ecosystem functioning.