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Phosphorus (P) transformations and associated changes in soil chemistry following lime application in acidic soils are very determinant to enhance P use efficiency. Thus, this study was conducted to evaluate the effects of different rates of lime on soil P fractions and chemical properties in acidic Luvisols of southern Ethiopia. The lime rates were 0 t/ha (0%), 3.75 t/ha (50%), 7.5 t/ha (100%), and 11.25 t/ha (150%), and incubated for a month with three replications. The soil P fractions analyzed includes soluble P (P-sol), P associated with iron (Fe-P), aluminum (Al-P), calcium (Ca-P), organic part (Org-P) and residual (Res-P). The result indicated that liming significantly (p < 0.05) improved the release of P-sol, Ca-P, and Res-P, and reduced Fe-P, Al-P, and Org-P. The changes in soil chemical properties were also significant. For instance, increased rate of lime enhanced soil pH from 5.3 to 6.5, reduced exchangeable acidity from 1.47 to 0.15 cmol(+)/kg, and increased available P from 2.74 to 8.72 cmol(+)/kg. Yet, the amount of P-sol was found low for plant needs even at a 150% rate of lime. Thus, working on external P requirement to equilibrate the need for plants followed by crop response validation are suggested. [ABSTRACT FROM AUTHOR]

This study investigated phosphorous (P) sorption characteristics under lime rates, and validated them under field conditions. Soil samples from nitisols and luvisols were taken, mixed with lime(tha−1) at[0,0], [5.25, 3.75], [10.5, 7.5] and [15.75, 11.25], respectively, and incubated for 30 days. It was equilibrated with KH2PO4 at 0, 10, 20, 30, 40, and 50 mgPL−1. The data were tested with Freundlich and Langmuir models. External P requirement (EPR) and changes in chemical properties were evaluated. The field validation on wheat involved rates of P (0, 8.2, 16.4, 24.6, 32.9, and 41.1 kg ha−1) and lime (0, 650, and 1300 kgha−1) in a randomized complete block design with three replications. Freundlich was found the best-fitted model. Freundlich coefficient (Kf) ranged from 212 to 45 mgPkg−1 (nitisols) whereas it was 112.7 to 16.29 mgPkg−1 (luvisols). EPR (kgPha−1) without and the highest lime rate were: nitisols (142.5 and 52.32 kgPha−1) and luvisols (124.84 and 25.94 kgPha−1). Liming reduced EPR by 63.3% (nitisols) and 79.3% (luvisols). Liming increased soil pH from [4.55 to 6.60 in the nitisols, and 5.33 to 6.51 in luvisols]; exchangeable acidity (cmol(+)kg−1) 3.84 to 0.01 nitisols, and 0.72–0.05 luvisols, and available P (mg/kg) 3.2–6.32 nitisol, and 2.74–8.72 luvisols. Furthermore, applying 32.9 kgPha−1 x 1300 kgha−1 lime resulted in grain yield (4345.2 kgha−1) that was 449% more than the untreated crop (791.3 kgha−1). The validation result suggested higher P than blanket P recommendation. It also justifies that excess P or lime alone cannot be a complete solution for P management and increased yield. [ABSTRACT FROM AUTHOR]