Introductory lecture. Development of humus research during the past Humus et Planta symposia (R. Apfelthaler). Section A Structure, physical and chemical properties of humus substances. Application of electron spin resonance and fluorescence spectroscopies to the study of soil humic substances (N. Senesi). Applications of pyrolysis-gas chromatography/mass spectrometry to the study of soils, plant materials and humic substances. A critical appraisal (C. Saiz- Jimenez). Section B Relationships among humus soils properties and fertility. Carbon and nitrogen dynamics in soil in long term field experiments (M. Korschens). The role of root properties and organic matter on mobilization of soil P and rock phosphates (A. Amberger). Influence of organic carbon and nitrogen associated with cropping history and soil textural class on nitrogen use by winter wheat (Triticum aestivum) (L.V. Vaidyanathan, W.S. Wilson). Effect of chemical properties of soil on humification of organic soil matter with respect to organic and mineral phosphorus fractions (L. Kolar, V. Riha, R. Tichy). Compensation for organic carbon loss from soil at nitrogen fertilizer application (V.N. Kudeyarov). Section C Biotransformations of organic substances in soil. Biotransformations in different climate belts; source - sink relationships (H.W. Scharpenseel, H.V. Neue, S.T. Singer). Availability of carbon and nitrogen contained in different soil and particle-size fractions (B. Nicolardot, D. Cheneby, M.R. Allard). The fertilizing value of waste waters from the olive processing industry (U. Tomati, E. Galli). Microbial degradation of plant materials and allelochemicals formation in different soils (W. Weyman-Kaczmarkowa, D. Wojcik- Wojtkowiak). Section D Relationships between humic substances and plants. Humic substances affect transport properties of root membranes (A. Maggioni, Z. Varanini, R. Pinton, M.G. de Biasi). Effect of natural substances on plants: biological control of telluric phytopathogenic fungi by an antifungal compost (O. Reisinger, S. Durecu, F. Toutain). Section E Interactions of humus and xenobiotic substances. Organic substrates and microbial conversion of herbicides in soil (F. Kunc). Prediction of the role of soil organic matter and some other soil characteristics in herbicide adsorption (J. Kozak, M. Valla, P. Prokopec, O. Vacek). Surveys of individual poster sessions. Humic substances, their structure, chemical and physical properties (M. Valla). Relationships between humus, soil properties and soil fertility (L. Kolar). Biotransformations of organic matter and nitrogen in soil (J. Novakova, M. Tesarova). Relationships between humus substances and plants (F. Pospisil). Interactions of humus and xenobiotic compounds (F. Kunc).