The nutrition of the world population in future needs an increase of plant production at locations of increasing requirements. For this, soil organic matter carries out very important contributions. Nitrogen supply for the plant is closely connected with the dynamics of the organic con stituents in soil. Formation, transformation and degradation of soil organic matter occur mainly by biochemical reactions, which have to be known to find out the causal connections with plant production. The processes that occur during formation of the fractions of humic sub stances in soil organic matter can...