Relationship between soil organic matter lability and liming requirement in acid sandy-loam cambisols

It is evident that the presence of organic matters in soil considerably influences by its microbial oxidation to CO2 the requirement for calcareous compounds as well as the necessary amelioration dose of lime to reduce incurred soil acidity as the impact of balanced buffering CO2-HCO3- system, the more labile the organic matters are. If we take into consideration that the content of soil water per hectare of topsoil is, at the total weight of 6 × 106 kg, approximately, in analyzed sandy-loam soils 1.2 × 106 litre, in the given experiment soil water is just able to use up to 220 kg CaCO3/ha for the fixation of free surplus CO2 to the value of equilibrium CO2, at zero elution! From this process, even 300-400 kg water-soluble Ca(HCO3)2 result. Of course, the ion exchange and the buffering system of the soil have further requirements for Ca compounds. Consequently, an unambiguous conclusion is: doses of calcareous compounds cannot be calculated only with the aim of reducing soil acidity and consumption of Ca nutrient by plants as it is common in the other nutrients. In a practical experiment in watersheds of nine Šumava brooks of the total area of 78.5 km2 we studied changes in the stability of soil organic matters in the soils of these brooks in relation to variations in calcium carbonate equilibriums in waters from these watersheds in 1986-2004. The loss of the least stable fraction of soil organic matters, and the associated loss of the microbial activity of soils, were found to lead to a decrease in Langelier saturation index Is in the waters, hence to a reduction in water corrosivity against CaCO3, and so to a smaller need of liming to establish the calcium carbonate equilibrium in soil solutions even though exchange and active acidity of soil increased.