Momentum of Re-Acidification Over Time in Lime Reclaimed Acidic Soil of Bako Area in Soybean (Glycine max L.) Production, Western Ethiopia

On station a permanent plot experiment was conducted at Bako during 2012-2015 cropping season to investigate soil acidity and P availability change over time in response to the application of different rates of agricultural lime to determine the optimal level and frequency of lime application in improving soybean productivity and selected chemical properties of the soil. Five levels of lime (0, 2.3, 3.45, 4.6, and 5.75 t/ha) were laid out in Randomized Complete Block Design with three replications. The results of the study showed that the highest grain yield was recorded from the use of slightly optimal 5.75 t/ha (125% recommended rate) level of lime. Similarly, grain yield was significantly affected by the cropping season where the maximum mean value was obtained in the second cropping season, improving soybean productivity by 148% compared to the control. In the other standpoint, the soil laboratory analytical results after harvest showed that the highest soil pH (6.22) was recorded from the application of optimal level (5.75 t/ha) of lime. Conversely, the exchangeable acidity was significantly reduced to 0.52 cmol(+)/kg that improved the potential acidity level of the soil by 196%. The highest soil available P (26.39 mg/kg of soil) was recorded from the plots treated with 4.6 tons/ha of lime in the second cropping season. The grain yield data and soil test results showed that both attributes were affected by the cropping season where optimal values were recorded during the second cropping season after lime application, which afterward witnessed a decreasing tendency starting from the third year after lime application indicating that the subsequent liming intervention should be made after the third year to sustain soil and soybean productivity of the area.

Keywords: Available P; Exchangeable acidity; Optimal level; Re-liming; Soil pH