The need for liming depends on the soil reaction (pH) and soil agronomic category (Table 1).
Soil reaction (pH) can be determined by laboratory methods or by a field pH meter.

Table 1. Assessment of soil liming requirements

The recommended lime doses depending on liming requirements are given in Table 2.

The lime doses in Table 2 were calculated in order to bring the soil reaction to an optimum value (Table 3). However, the total lime dose calculated for the “liming necessary” range is not recommended because of the possible “over-liming” effect, i.e. impairment of plant nutrient availability. The maximum doses of CaO to be applied at one time are shown in brackets. The lime treatment with a supplementary dose can be repeated after a year, after determining the current pH value of the soil.

Table 2. Lime doses on arable land in tonnes CaO per ha

The doses of fertiliser lime are customarily expressed in tonnes of calcium oxide per hectare. The farmer is required to convert the appropriate dosage from Table 2 to the dosage of the specific fertilizer lime, taking into account the percentage of CaO in the lime. There are many types of fertilizer lime available on the market. A distinction is made between oxide lime fertilisers (containing CaO) and carbonate lime fertilisers (containing CaCO3) depending on the form in which the lime is present. In both types of lime, the calcium content is expressed as calcium oxide (CaO). Above approach makes the conversion of the recommended amount of CaO into fertiliser the same. For example, if the recommended dose according to table 1 is 2t CaO/ha and you have a lime fertiliser with a CaO content of 50%, then to achieve the desired effect, you need to apply 2t CaO/ha : (50% CaO/100) = 4t fertiliser weight per hectare.

Table 3. Optimum pH values for agronomic soil categories