This volume presents the proceedings of the 10th internationalsymposium Humus et Planta held in Prague in August 19-23,1991. The main topics of this book are devoted to the recentadvances in fundamental, as well as applied research of humicsubstances, the most abundant of the naturally occuringmacromolecules of nature, the understanding of their natureand how they react and interact in their natural environments.Texts are included on the structure, physical and chemicalproperties of humic substances; the relationships among humus,soil properties and fertility; the biotransformations oforganic substances in the soil; the relationships betweenhumic substances and plants and the interactions of humus andxenobiotic substances. This book presents recent knowledge ofthe complicated and challenging humic substances. It will beof interest not only to scientist, but also to Universityteachers and students of agricultural and environmentalsciences.