The agronomic effectiveness of biofertilizers is influenced by strain origin, genetic identity, crop genotype, soil type, and environmental conditions. For best results, both the plant and rhizobia strain must be adapted to the common harsh soil conditions in the tropics. While plant varieties have changed over the years, complementary research on new strains effectiveness under varying soil fertility conditions has lagged in southern Africa. Seven field experiments were established in the main soybean-producing areas of Zimbabwe in the north, central, and north–east regions to evaluate agronomic benefits of new rhizobia strains against the current exotic commercial strain (MAR1491). One site was irrigated (site 3), and the other six sites were rainfed (sites 1, 2, 4, 5, 6, and 7). While trends in inoculation response varied from site to site due to site conditions, inoculation with the strains NAZ15, NAZ25, and NAK128 consistently yielded high grain yields, which were similar to the current commercial strain MAR1491 and to application of mineral fertilizer (51.75 and 100 kg N ha⁻¹). Grain yield levels were generally below 2 t ha⁻¹ for sites 2, 3, and 5 and above 2 t ha⁻¹ for sites 1, 4, and 6, while for the irrigated site 3, they ranged upwards of 3 t ha⁻¹. When irrigated, all strains except NAK9 performed similarly in terms of grain yields and aboveground N uptake. Further testing on the inclusion of the indigenous strains NAZ15, NAZ25, and NAK128 in multi-strain commercial inoculant production targeting application in regions and soils where they excel beyond the current exotic strain MAR1491 is recommended.

Agronomic effectiveness of biofertilizers is influenced by strain origin, genetic identity, crop genotype, soil type and environmental conditions. For best results both the plant and rhizobia strain must be adapted to the common harsh soil conditions. While plant varieties have changed over the years, complementary research on new strains effectiveness under varying soil fertility conditions has lagged in southern Africa. Seven field experiments were established in the main soybean producing areas of Zimbabwe in the north, central and north-east regions to evaluate agronomic benefits of new rhizobia strains against the current exotic commercial strain (MAR 1491). One site was irrigated (site 3) and the other six sites were rainfed (site 1, 2, 4, 5, 6, and 7). While trends in inoculation response varied from site to site due to site conditions, inoculation with the strains NAZ15, NAZ 25, and NAK128 consistently yielded high grain yields which were similar to the current commercial strain MAR 1491 and to application of mineral fertilizer (51.75 and 100 kg N ha-1). Grain yield levels were generally below 2 t ha-1 for site 2, 3, and 5, above 2t ha-1 for sites 1, 4, and 6, while for the irrigated site 3 they ranged upwards of 3 t ha-1. When irrigated all strains except NAK9 performed similarly in terms of grain yields and aboveground N uptake. We recommend further testing on the inclusion of the indigenous strains NAZ15, NAZ 25 and NAK128 in multi-strain commercial inoculant production targeting application in regions and soils where they excel beyond the current exotic strain MAR 1491.

Soil phosphorus deficiency and the high cost of mineral fertilizers necessitate research into alternative strategies. Inoculating seeds with adapted phosphorus‐solubilizing microorganisms (PSMs) could be a cost‐effective option. This study explored diversity, including phenotypic and genotypic characteristics of PSMs from selected soils and cropping systems of Zimbabwe, for coapplication with rock phosphate (RP). Culturable PSMs were isolated from preincubated or cowpea rhizosphere soil. Over 91% of the 37 isolates (PSM1–PSM37) were bacteria, while 8% were fungi. Diversity was higher in Dorowa ( H′ 2.99; DMn 8.49) than that in Marondera ( H′ 2.85; DMn 7.57), and under groundnut and maize ( H′ 3.26) than other crops. Some PSMs occurred only in Marondera (8%) and Dorowa (14%). The P solubilization index on RP‐amended Pikovskaya medium, ranged between 1.00 and 15.9. Sixty‐five percent of the best 28 isolates were Gram‐negative cocci or bacilli, while 35% were Gram‐positive cocci. A dendrogram based on morphological, biochemical, and functional characterization grouped the isolates into two major clusters and four subgroups. On the basis of 16S recombinant DNA analyses, the Bacillus genus predominated (61%), with the highest P solubilization capacity ( Bacillus amyloliquefaciens ), while the rest (39%) were Enterobacter , Microbacterium , Paenibacillus, Klebsiella , Priestia , Acinetobacter , Nocardioides , and Kocuria genera. In conclusion, studied soils harbor diverse PSMs that solubilize RP, indicating their potential to develop affordable bioinoculants for improved productivity on P‐limited soils. The study pioneers the discovery of diverse PSMs native to Zimbabwean soils. Further studies are required to evaluate PSM–RP efficacy with various crops under glasshouse and field conditions and benchmark with conventional fertilizers.