Effect of Lime rates and Incubation Periods on the amelioration of Acidic Nitisols of Bedi area in Ethiopia

A study was conducted to determine the optimum lime/CaCO₃ rate and incubation period and exchangeable acidity equivalence for the amelioration of acidic nitisols collected from the central highlands of Ethiopia. A pot experiment was conducted at Holeta Agricultural Research Centre (HARC) in lath house using acidic soil samples collected from a depth of 0-20 cm from Bedi area, central high lands of Ethiopia. The treatments consisted of factorial combination of lime rates (0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 mg kg soil) and different incubation periods (7, 14, 21, 28, 35, 42 days). The treatments were arranged in RCBD with two replications. The result of the study showed that the soil pH consistently increased with the increase in lime application rates. There is no clear trend of incubation period effect on soil pH but higher pH was recorded after four weeks of incubation following lime application indicating that lime incubation period for optimization of soil pH would be one month before planting, if soil moisture level is kept optimum. The results showed that incubation method of calibrating soil pH using lime/ calcite completely changes soil pH from extremely acidic (3.85) to near optimum pH of 6 or 6.5 suitable for crop production. Incubation method ends up in higher rates of lime application compared to the exchangeable acidity based method. Results of the current incubation method study revealed that 12.6 and 16.8 t ha^-1 needs to be applied to raise the soil pH from 3.85 to 6 or 6.5 which has to be applied four weeks before planning.