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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]

The objective of the study was to evaluate effects of liming on phosphorus (P) adsorption and desorption capacity of acid soils in Assosa and Bambasi Districts. The soil samples were collected from six rural Kebeles; three from each Kebele and totally 18 samples were collected. The study was conducted in accordance with batch equilibrium method and adsorption values were fitted to Langmuir, Freundlich, and Temkin models to evaluate the goodness of curve fit. Differences between the models' indices and soil property parameters were analyzed by analysis of variance (ANOVA). The study revealed that unlimed soils of Amba-7, Sonka, and Amba-1 sites had higher range of P-sorption maxima (416.7–500.0 mg/kg) than the limed ones. In addition, the limed soils had shown lower adsorption maxima than the unlimed soils based on the Langmuir model. According to Freundlich model, limed soils had a lower Kf value than the unlimed soils. Similarly, Temkin model also verified that unlimed soils had higher b value (sorption energy) than limed soils. Total P desorbed (TPD) value of limed soils had shown a significant difference (p =.022) between the soils of different sites; then soils of Amba-16, Amba-7 and Sonka had relatively higher TPD value than the soils of the left sites. On lime treated soils the total P desorbed had shown increment relative to the untreated soils. The P-sorption isotherm was fitted best to Temkin model than the Langmuir and Freundlich models. Soils of the study area require liming to improve the P-adsorption problem; especially soils of Amba-7, Sonka, and Amba-1. [ABSTRACT FROM AUTHOR]