Preface

The SOM is an important prerequisite for soil formation, soil fertility, yield and environmental protection. Improved systems of soil utilisation and management can contribute to protection of the environment. For almost all nutrients and pollutants in agricultural soils the threshold values have been elaborated. They have already been largely applied in practice. For the most important nutrients, carbon and nitrogen in soil, such threshold values have not been elaborated, yet. Just first approaches aiming at the estimation of the optimum organic carbon and nitrogen contents in arable soils have been done. Results of the past extensive research in humus chemistry hardly came out from the stage of the basic research. For this reason, an international working group "Practical Solutions for Managing optimum C and N in Agricultural Soils" has been established in 1998. The annual convention 2000 and 2001 took place in the Research Institute of Crop Production in Prague - Ruzyne, in which a long tradition in organising scientific meetings on a similar subject already exists. A series of HUMUS ET PLANTA conferences should be mentioned at this place. Prague has also a favourable geographical position in Europe and special advantages as a place of scientific meetings. The most important contributions to the conference are arranged in this edition.