Abstract Description

Soil microbial communities are key drivers of nutrient cycling, soil health, and crop productivity, yet their structure and diversity remain understudied in many regions of South Africa. This study explored how different fertilisation regimes influence microbial diversity in agricultural soils of Tzaneen, Limpopo. Soil samples were collected from seven farms with varying fertiliser practices (organic, chemical, or mixed), and next-generation sequencing (NGS) was used to profile bacterial and fungal communities. Proteobacteria, Actinobacteria, and Firmicutes emerged as dominant bacterial phyla, while Ascomycota was the most abundant fungal group. Sites using organic fertilisers showed consistently higher microbial diversity, suggesting that organic inputs foster more robust and diverse microbiomes. In addition, several plant growth-promoting bacteria (PGPB), including Priestia megaterium and Achromobacter marplatensis were identified. Conversely, soils under exclusive chemical fertilisation harboured lower microbial diversity and a higher occurrence of fungal pathogens, such as Fusarium oxysporum. These findings suggest a link between fertilisation type and both beneficial and harmful microbial populations. These findings offer valuable insights into soil microbial ecology in the region and support future development of microbiome-informed strategies for sustainable farming