Low pH and phosphorus are among major soil chemical constraints to Biological Nitrogen Fixation (BNF) and soybean production in sub-Saharan Africa. A screenhouse pot experiment was conducted at Sokoine University of Agriculture- Morogoro Tanzania, to examine the ameliorating effect of liming to pH, phosphorus uptake, BNF and yield of soybean grown on an ultisol. The experiment was a 33 factorial laid out as a split plot with two replications. Source of nitrogen (inoculation, non-inoculation and applied inorganic nitrogen) was main plot factor, while the subplots received combinations of lime and phosphorus. The levels of lime used for the incubation experiment were 0, 5 and 10 ton ha-1 while those of P were 0, 50 and 100 kg*ha-1. A commercial inoculant-Legumefix, was used for inoculation. Results indicated that liming significantly (P<0.05) raised the soil pH and that the interaction of lime and phosphorus showed significant (P<0.05) effect on nodulation and N2 fixation. Overall, application of 5 tons of lime per ha-1 and 100 kg P*ha-1 gave the best case scenario in terms of pH amelioration, P availability and BNF enhancement by the soybean-Bradyrhizobium symbiosis.

Limited solubility of the Tanzania’s Minjingu phosphate rock (MPR) in non-acidic soil conditions has held back its potential for widespread use in agricultural production. This study was designed to isolate, characterize and test phosphate-solubilizing bacteria for their potential to increase solubility of MPR and enhance maize plant growth under field conditions. Ten out of 19 isolates showing greatest phosphate solubilization indices on a Pikovskaya agar medium were further characterized for other plant-growth promoting traits including production of IAA, siderophores and ammonia. Two of them, namely isolates-MdE4 and MdG1 substantially outperformed other isolates in phosphate solubilization and production of IAA, ammonia and siderophores. The two isolates molecularly identified as Klebsiella variicola-MdE4 and K. variicola-MdG1 produced up 701, 699 and 750, 680 μg/ml of soluble phosphate from tricalcium phosphate and hard Minjungu rock phosphate, respectively. Additionally, Biorock P- a biofertilizer formulation containing MdE4 and MdG1 co-cultured in a molasses-based modified broth medium retained most of the phosphate solubilizing potential and other plant-growth promoting traits of MdE4 and MdG1. Co-application of MdE1 and MdG1-containing “bio-rock P” and inorganic phosphate at 20 kg P/ha resulted in higher maize grain yield than that of positive control (40 kg P/ha) under field conditions. The two isolates- Klebsiella variicola-MdE4 and K. variicola-MdG1 have the potential for use in a biofertilizer formulation for commercial field applications.

This study aimed to isolate and identify phosphate solubilizing microorganisms from rhizosphere soils and evaluate their plant growth-promoting traits in vitro. Fifty-six potential phosphate-solubilizing bacteria were isolated, and ten isolates were selected for further characterization based on their performance. Burkholderia species were found to be the predominant solubilizers of insoluble phosphorus sources. Two strains, B. vietnamiensis-OP984178 and B. ambifaria-OP984173, showed the ability to release soluble phosphorus from different sources, including tricalcium phosphate, ferric phosphate, and hard Minjingu rock phosphate powder. Both isolates also demonstrated production of indole acetic acid, with B. vietnamiensis-OP984178 and B. ambifaria-OP984173 producing up to 23.45 μg/ml and 24.24 μg/ml, respectively. Furthermore, the strains showed antifungal efficiencies of 31.48% and 24.81%, respectively, when co-inoculated with Fusarium proliferatum-MZ497514 on potato dextrose agar. The study also identified the nitrogen fixation potential of the two strains. Overall, the findings highlight the potential of the selected Burkholderia strains as biofertilizers and biocontrol agents, making them valuable candidates for sustainable agriculture practices. Further research is recommended to explore the potential of these strains using test crops.

Irish potato (Solanum tuberosum) is a critical crop for food security and economic growth in Tsangano and Angónia districts, central Mozambique. Challenges like inconsistent yields and variable quality are often linked to suboptimal soil conditions, and limit production. This study aimed to classify and evaluate the suitability of soils for potato cultivation, filling gaps in detailed soil assessments for sustainable agriculture. Using combined pedological approach and laboratory soil analysis, four pedons TSA-P01 and TSA-P02 in Tsangano, and ANGO-P01 and ANGO-P02 in Angónia were analyzed for bulk density, texture, pH, organic carbon, and nutrient content. The pedons were very deep (> 150 cm) and had textures ranging from sandy clay loam to sandy loam. TSA-P02 had the lowest bulk density (0.78 Mg m-3) and the highest available water capacity (182.0 mm m-1). Soil pH ranged from 5.6 to 7.9, indicating neutral to slightly acidic conditions. Nutrient analysis revealed low total nitrogen (0.12 - 0.22%), varying soil organic carbon (0.16 - 2.73%), and cation exchange capacity (10.1 - 11.33 cmol(+) kg-1). Pedons TSA-P01, ANGO-P1, and ANGO-P02 were characterized by eluviation and illuviation as dominant pedogenic processes while in pedon TSA-P02 shrinking and swelling were the pedo-genic processes. Weathering indices identified ANGO-P01 as the most highly weathered, while TSA-P02 was the least weathered and had better fertility indicators. According to USDA Taxonomy, the soils were classified as Ultisols, Vertisols, and Alfisols, corresponding to Acrisols, Alisols, Vertisols, and Luvisols in the WRB for Soil Resources. All studied soils were marginally suitable for potato production (S3f) due to dominant fertility constraints but with varying minor limitations in climate, topography, and soil physical properties. The findings hence recommended targeted soil fertility management to enhance productivity and sustainability in potato cultivation.