RAMETO WABELA BUSER2026-01-282026https://etd.hu.edu.et/handle/123456789/315Declining soil fertility is a major challenge for crop production in southern Ethiopia. Despite the potential of integrated soil fertility management (ISFM), its effects on soil properties and common beans yield remain inadequately investigated. Therefore, this study was conducted to (1) characterize and classify soils at selected sites, (2) assess P sorption characteristics and the effects of ISFM on P sorption characteristics, (3) quantify native rhizobia populations capable of nodulating common beans, and (4) evaluate the effects of integrated application of inorganic, organic, and biofertilizer on soil properties and yield components of common beans. The research was carried out in three sites of southern Ethiopia: Kokate, Hawassa, and Alage. Three profiles, one from each experimental site, were excavated and characterized. In total, 27 soil samples were collected (9 composite surface samples and 18 from distinct horizons) and analyzed for morphological, physical, and chemical properties. Phosphorus sorption isotherms of study soils were determined by batch equilibrium methods, using the Langmuir and xx Freundlich models. After the incubation experiment, a laboratory analysis was conducted to evaluate the impact of ISFM on the P sorption characteristics of soils collected from each site. For this study, 54 composite soil samples were collected (6 treatments x 3 replications x 3 sites). Native rhizobia abundance was assessed through laboratory and lath house experiments in 2021–2022 using the most probable number (MPN) technique. The pot experiment in the lath house used commercial rhizobia inoculant and inorganic nitrogen fertilizer as treatments, arranged in a completely randomized design (CRD). A total of 27 composite soil samples were collected for the present study (3 composites * 3 sites * 3 replications). Finally, field experiments were conducted for two consecutive cropping seasons (2021 and 2022) at all sites, arranged in RCBD design with three replications. The treatments included three levels of inorganic p fertilizer (0, 8.5, and 17 kg P ha⁻1 for Kokate; 0, 5.8, and 11.6 kg P ha⁻1 for Hawassa; and 0, 7.1, and 14.2 kg P ha⁻1 for Alage) combined with organic amendments (biochar or compost) and biofertilizer. The studied soils showed great heterogeneity in their properties. Based on WRB, the soils were classified as Luvisols (Kokate), Cambisols (Hawassa), and Fluvisols (Alage). This variability highlights the need for site-specific management practices. The analysis of P sorption showed that the Freundlich model better described P sorption characteristic than the Langmuir model. Among the soils, Luvisols had the highest P sorption capacity, while Cambisols had the lowest. Application of ISFM, such as biochar with inorganic P fertilizer in Luvisols and compost with inorganic P fertilizer in Cambisols and Fluvisols, significantly reduced P-sorption capacity. Native rhizobia populations capable of nodulating common beans varied significantly across sites. The lowest counts were found in Kokate, while Hawassa had the highest. Rhizobia abundance was strongly correlated with soil properties, cropping history, and bean yield components. Both inoculation and inorganic N fertilizer increased yield components, and their xxi combination gave the highest yield. Relative symbiotic effectiveness ranged from 47% in Kokate to 67% in Hawassa, while absolute symbiotic efficiency varied between 76% and 144%. The commercial Rhizobium was more effective in soils with higher native rhizobia populations (Hawassa and Alage) compared to Kokate, where native rhizobia populations were low. Field experiment results confirmed that ISFM significantly improved soil properties and common bean yields. The integrated application of inorganic P fertilizers, organic inputs (compost or biochar), and biofertilizers increased soil pH, SOC, and avail P. Grain yields increase by 23% in Hawassa and 24% in Alage with the combined use of compost (5 t ha-1 ) with 11.6 and 14.2 kg ha-1 P fertilizer,respectively. In Kokate, combining biochar (5 t ha-1 ) with 17 kg P ha-1 fertilizer increased yield by 18%. Economic analysis revealed that ISFM practices were more profitable than single type of fertilizer use. The most profitable options were 5.8 and 7.1 kg P ha-1 + 5 t ha1 compost in Hawassa and Alage and 17 kg P ha-1 + 5 t ha-1 biochar in Kokate. Overall, the initial fertility status of the soils was characterized by medium SOC and TN but low avail P and micronutrients, indicating generally low soil fertility. The results showed that site-specific ISFM practices can substantially improve soil fertility, crop yields, and profitability of common bean production in southern Ethiopia. This confirms that a “one-size-fits-all” approach is ineffective due to high soil variability, and tailored strategies are needed for sustainable common bean production in southern Ethiopia.en-USAbundanceBiocharCompostCrop yieldFreundlich P sorptionProfileRhizobiaSoil classificationThesis