Bacterial Diversity Dynamics in Sandy Loam Soils in Tanzania Under Varying Fertilizer-Derived Uranium Concentrations
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Date
2025-08-13
Journal Title
Journal ISSN
Volume Title
Publisher
Microorganisms
Abstract
The presence of radiotoxic uranium (U) in mineral fertilizers is of global concern. A pilot
study was conducted in Tabora (Tanzania) to determine the release of U from three brands
of phosphate fertilizers and its impact on soil bacteria. The experiment used three types
of fertilizer: Minjingu Powder (MP), Nafaka Plus (NP), a mixed and granulated fertilizer
made from Minjingu Phosphate Rock (MPR), and YaraMila Cereal (YC) fertilizer. There was
also a control treatment that was not fertilized (NF). Alpha diversity and the R tool were
used to analyze bacterial diversity in four samples within an average sequencing depth
of 74,466 reads, using metrics like ASVs, Shannon index, and Chao1. The results showed
that the number of amplicon sequence variants (ASVs) in the DNA from soil bacteria
decreased, specifically to 400 ASVs, in the NP treatment, which was in line with the higher U
concentration (3.93 mg kg−1) in the soils. In contrast, the MP fertilizer treatment, associated
with a lower U concentration (3.06 mg kg−1) in soils, exhibited an increase in ASVs within
the DNA of soil bacteria, reaching 795; the highest ASV value (822) was observed in the NF
treatment. Higher amounts of U in the soil plots seemed to have resulted in more types of
bacteria, with the Actinobacteriota phylum being the most common in all of the treatments.
The NP (3.93 mg kg−3 U concentration) and MP (3.06 mg kg−3 U concentration) treatments
were the only ones that showed Halobacteriota and Crenarchaeota phyla. Nonetheless,
bacterial diversity may also account for the alterations in soil phosphorus and nitrogen
following fertilizer application. The YaraMila Cereal treatment did not seem to be linked
to any particular bacterial phylum. This means that in this study it did not have any
measurable effect on the soil bacteria species compared to the MP and NP treatments
Sustainable Development Goals
SDG - 2 : Zero Hunger
SDG - 3 : Good Health and Well‑being
SDG - 6 : Clean Water and Sanitation
SDG - 9 : Industry, Innovation and Infrastructure (research & monitoring)
SDG -12 : Responsible Consumption and Production
Keywords
uranium, soil bacterial diversity, loam soil, phosphate fertilizers