PhD & Postdoc

Naomi Mwangi

Soil Microbiome Engineering · Kenyatta University

Naomi Mwangi designs synthetic microbial consortia — combining nitrogen-fixing bacteria with phosphate-solubilising fungi and plant-growth-promoting rhizobacteria — to substitute synthetic nitrogen fertiliser in the smallholder maize-bean intercropping systems that dominate Kenya's central highlands, where ferralsol soil acidity and low phosphorus availability limit both biological nitrogen fixation and crop productivity. At Kenyatta University's Department of Agricultural Sciences, supervised by Prof. Joseph Njeru, she has isolated and characterised 84 strains from rhizosphere soils across four agro-ecological zones using 16S rRNA sequencing, acetylene-reduction assays, and PGPR functional trait screening. Her best four-strain consortium — a Bradyrhizobium japonicum strain paired with Rhizobium leguminosarum, Trichoderma asperellum, and Bacillus subtilis — was formulated as a peat-based seed inoculant and field-tested across 24 smallholder plots in Embu and Murang'a counties. ¹⁵N isotope dilution measurements over two seasons confirm a 34% increase in biological nitrogen fixation in bean and 19% increase in maize grain yield over the uninoculated control without additional synthetic N fertiliser. Naomi's partnership with the CGIAR Eastern Africa maize programme provides multi-location trial infrastructure across Kenya, Tanzania, and Ethiopia, significantly extending her dataset beyond what a single university can support.

Thesis Topic

Synthetic Microbial Consortia Inoculants for Nitrogen Fixation Enhancement in Smallholder Maize-Bean Intercropping Systems on Kenyan Ferralsols

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