Liming is carried out by application of CaCO3 in limestone, a process that is described in some detail in Troeh and Thompson (98). The neutralizing capacity of the limestone used is measured by comparing it to calcite, which is CaCO3, with a calcium carbonate equivalent (CCE) of 100%. The fineness of the lime affects its efficiency for liming, and the CCE and fineness and hardness of the lime together give the effective calcium carbonate equivalent or reactivity. Application should occur when the soil is dry or frozen, to avoid damage to the soil by the vehicles carrying the lime. Although soil testing will determine if an application is required, it is often the practice to apply lime a year ahead of a crop in a rotation that has a strong lime requirement (often a legume). An application once every 4 to 8 years is usually effective. Limestone, burned lime (CaO), or slaked lime [Ca(OH)2] can also be used. Burned lime has a CCE of 179% and slaked lime a CCE of 133%.
In the pH-base saturation method, the percent base saturation of the soil, the CEC of the soil and the initial pH all have to be measured. To calculate how much lime should be added the percent base saturation at the initial and at the target pH value are read off a graph, and the amount of CaCO3 to be added is calculated from the difference in percent base saturation at the two pH values multiplied by the CEC (98).
In the buffer solution method, a sample of the soil is mixed with a buffer, and the amount of lime required is read off a table from the value of decrease in buffer pH on adding the soil (120).
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