A SIMPLIFIED APPROACH TO LIMING AND ITS EVALUATION

Abstract

Lime requirement is based on determination of soil acidity and CEC in a representative sample of soil from the land profile (regularly from topsoil). Acidity is measured in a suspension of soil and 0.2 M KCl solution at a 1:1 ratio (w/v); CEC determination is a part of the multinutrient soil test KVK-UF. A desired range of soil pH values is defined in relation to CEC value (mmol+ kg−1). Desired pH values of soil are calculated from these relations: pH(lower)=2.9×CEC0.14, pH(upper)=3×CEC0.146. A difference between the defined and calculated desired pH is used as the basis for determining lime requirement (CaCO3 t ha−1), and is dependent upon soil buffering capacity, which is closely related to CEC. Information on the depth of sampled profile, bulk density of soil, and skeleton proportion (particles>2 mm) is used for further specification of lime requirement. Recommendation of a maximum single lime application rate related to CEC is also a part of the liming model. To evaluate the liming model function 15-week incubation experiments with differentiated rates of CaCO3 and CaO (equivalent to 1.5 to 9.0 t CaCO3 ha−1) were carried out on seven soils with naturally low pH. The goal of these observations was to determine changes in soil acidity (pH-H2O, 0.01 M CaCl2, 0.2 M KCl and 1 M KCl), concentrations of extractable aluminum, accumulation of mineral nitrogen forms (NH4 + and NO3 −) and organic solutes in soil, and availability of nutrients from the soil by means of plant tissue analyses (barley and mustard). The liming rates providing for the lower desired pH value were fully sufficient with respect to the appropriate depression of aluminum. Liming, also considerably decreased manganese availability. There was a large depression of boron availability in all soils when low liming doses below the lower pH value were applied. Liming rates that exceeded the desired pH range were related to an increase in nitrification, which was especially high in soils with the extremely low starting pH value. The experimental results also indicate the usefulness of information on the value of Mn soil test and the boron status in the soil in order to specify the liming rate.