Background: Though soils in the study areas are characterized by higher iron and aluminum oxides, and low available P contents, study on P adsorption characteristics is limited. The purpose of this experiment was to evaluate adsorption properties of selected soils and determine the standard phosphorous requirements of the soils. In this experiment, separately weighed 2 g soil samples were equilibrated in 50 ml of 0.01 M CaCl 2 solution containing KH 2 PO 4 at rates of 0, 1, 2.0, 4.0, 8.0, 16.0, 24.0, and 32.0 mg P L −1 .Results: The Freundlich model was found to be the best model for the description of the P adsorption characteristics of the soils. The Freundlich coefficient K f ranged from 123.32 to 315.31 mg P kg −1 . The Goha-1 soil had the highest K f (315.31 mg P kg −1 ) as Ketasire had lowest K f (123.32 mg P kg −1 ) values. The value of SPR f was ranged from 50.50 to 154.02 mg P kg −1 for soils of the study area. Highly significant (P ≤ 0.01) correlation was observed between the Freundlich adsorption parameters and soil physicochemical properties. Conclusion:The standard P requirement of the studied soils was higher than the blanket P fertilizer rate recommendations in Ethiopia. Lack of inadequate knowledge about internal and external P requirement of each crop might have decreased yield in the study areas as it could have resulted in under-application of fertilizer P. The presence of high correlation between the adsorption parameters and the soil properties suggested the indices' prominent role in explaining P adsorption characteristics of the soils. Since higher dose of P is required by soils in the study area because of fixation, alternative P management strategies is needed to reduce P adsorption and enhance P availability. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

photocatalyst was successfully synthesized by sol-gel method using metal salts as precursors in the presence of acid catalyst. The as-synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), atomic absorption spectroscopy (AAS) and UV-Vis diffuse reflectance spectroscopy. Elemental analyses of the assynthesized samples were similar to those expected from the initial concentrations of the solutions used during synthesis. The x-ray diffraction pattern indicated that all as-synthesized samples had a crystal size with a rhombohedral structure and finest particle size of the catalyst (20.096 nm) was obtained at 400°C calcination temperature. The band gap energy of the MnO 2 /Al 2 O 3 /Fe 2 O 3 photocatalyst was calculated to be 1.97 eV and indicated that the as-synthesize sample had high photoabsorption property in the visible light region. Fourier transform infrared spectra confirmed the presence of hydroxyl group and Fe-O bond vibration in the catalyst. Experimental result of the MnO 2 /Al 2 O 3 /Fe 2 O 3 photocatalyst calcined at 400°C in 180 min (the molar ratio of 10 wt% Mn/15 wt% Al/75 wt% Fe) exhibited high photocatalytic activity of 92.89% under visible light irradiation. This may be due to the coupling effect of semiconductors, small particle size of catalyst and low electron-hole pair recombination on the surface of the catalyst. The pseudo-first-order rate constants of MG dye degradation in the presence of the catalyst were calculated as 4 × 10 -4 , 6.56 × 10 -3 and 1.0 × 10 -2 min -1 under no light irradiation, UV and visible light irradiation, respectively.

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