capacity, the acid-base buffering potential of soils, the adsorption properties, the behavior of micronutrients and heavy metals. Acidification of the environment increases because of industrial activity, urbanization and intensive soil use. Soil pH influences physical, chemical and biological properties of the soils. The rate of acidification of soils depends on the quality and quantity of the buffer systems present. The main buffer systems operating in the soils are variable charged surfaces of the soil colloids, humic substances, surface of AI(III)- and Fe(lII)-hydroxides, break surfaces of clay minerals, polymers of aluminum-hydroxides, -CaCC>3 -Ca(HC03)2 -H2CO3 system (Filep and Redly, 1990). In consequence of soil acidification the solubility of micronutrients and heavy metal ions changes. These soluble metal ions react with organic and mineral constituents of soils. Humic and fulvic acids are the main reactive natural organic polymers in the soils and natural waters they play very complex and important role in the soils. These organic acids are a very reactive part of the transformed organic materials. Their carboxyl and phenolic hydroxyl groups are responsible for the acidic-base properties. They as ligands can interact with metal ions (such as Cu, Mn, AL.) to form metal complexes (van Dijk, 1971 and Zunino, 1979). The aim of the examination is to study acid-base buffering properties of some soils, complexation of natural organic ligands with metal ions. Natural organic acids consist of a mixture of well- and ill-defined organic acids, the structure and chemical behavior of the ill defined organic acids is very complex.