Abstract: | A combination of thermal analyses and 15N tracer technique for investigation of humic acids Differences in humic acids of two extreme variants of three long-term trials due to a three years intensive fertilization in a pot experiment are also to be found by means of thermogravimetry. Additionally the 15N contents of humic acids were investigated at certain temperatures according to the peaks given by thermogravimetric study. The 15N isotope is also incorporated in higher molecular compounds. The 15N content varies due to differences in humus content and composition of the soils used. |