Rhizosphere Microbial Community Composition and Its Relationship to Crop Productivity in Nigerian Soil Types

This study characterises rhizosphere microbial community composition in major Nigerian soil types and examines the relationship between microbial community structure and crop productivity outcomes. Rhizosphere microorganisms including nitrogen fixers, phosphorus solubilisers, and plant growth-promoting bacteria are fundamental to nutrient cycling and crop growth, but the composition and functional potential of microbial communities in Nigerian agricultural soils are poorly characterised. This study collects rhizosphere soil samples from maize and cowpea plots on six contrasting soil types, representing ferruginous soils of the savanna, hydromorphic soils of the floodplains, ultisols of the Southeast, vertisols of Borno State, and alluvial soils of the Niger Delta, alongside bulk soil and bare soil controls. 16S rRNA amplicon sequencing is used to characterise bacterial community composition and diversity. Functional gene markers for nitrogen fixation (nifH), phosphorus solubilisation (pqq), and nitrification (amoA) are quantified by qPCR. Correlation and regression analyses link microbial community indices to crop yield and nutrient uptake data. Findings reveal significant soil type-specific differences in rhizosphere microbial diversity, with the highest functional gene abundance in alluvial soils of the Niger Delta. Soil organic carbon is the strongest predictor of total microbial biomass across soil types. The abundance of phosphorus-solubilising bacteria is significantly correlated with plant available phosphorus and crop phosphorus uptake in low-P soils. The study contributes original Nigerian rhizosphere microbiome data and recommends targeted biostimulant product development based on the identified functional gene profiles.

Keywords: rhizosphere microbiome, 16S rRNA sequencing, soil types, Nigeria, plant growth-promoting bacteria.