Pedological characterization and classification of soils is key for land resource planning and development of soil management interventions for improving agricultural productivity. A study was conducted in Bubi area of Lupane District, Zimbabwe, to examine soil morphological, physical and chemical attributes and to classify soils for land use planning and determining area specific soil management strategies. A detailed soil survey was conducted using a free survey method. Five soil mapping units M1, M2, M3, M4 and M5 were delineated and mapped based on field observations and laboratory analysis results. Soil samples were collected from representative profiles of each mapping unit for soil physical and chemical analyses. Sandy and loamy sand textures were dominant for surface soils while sandy clay loam and sands were dominant in subsurface soils. Mapping unit M3 had an abruptic textural change with sandy surface textures overlying sandy clay loam subsurface soils. Soil pH was alkaline (7.0 – 7.4) in deeper subsurface layers of M1, M2 and M4 mapping units. Exchangeable magnesium (Mg²⁺) and calcium (Ca²⁺) were the dominant exchangeable cations. The level of exchangeable Ca²⁺ for both surface and subsurface soils was low (< 5 cmol(+)kg^-1). Clay content had highly significant positive correlations with cation exchange capacity (CEC), exchangeable Ca²⁺, Mg²⁺ and soil pH. CEC had highly significant positive correlations with silt, soil pH, exchangeable Ca²⁺, Mg²⁺ and Na⁺. According to the ‘World Reference Base for Soil Resources’ classification system, soil units M1, M2, M3, M4 and M5 were classified as Calcic VERTISOLS, Haplic LUVISOLS, Haplic LIXISOLS (abruptic), Luvic CALCISOLS (Chromic) and Rubic ARENOSOLS (dystric) respectively. Clay content and CEC significantly correlated with most soil chemical properties in the study area. Liming, split fertilizer application and organic matter additions was recommended to address fertility issues related to high sand content, soil acidity, low CEC, low exchangeable Ca²⁺ and K⁺ constraints identified in some mapping units.

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.