A COMBINATION OF THERMAL ANALYSES AND N-1 5 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 experimen t are also to be found by means of thermogravimetry. Additionally the N-15 contents of humic acids were investigated at certain temperatures according to the peaks given by thermogravimetric study. The N-15 iso tope is also incorporated in higher molecular compounds. The N-15 cont ent varies due to differences in humus content and composition of the soils used.