Year-to year changes of soil organic matter (SOM) have been surveyed in a long-term
experiment in order to allow for crop/cropping system impact assessment. Legumes
usually caused SOM build-up, which on the other hand only to a short extend
remained during the succeeding years. Considerable SOM decrease could be found
under potatoes. SOM dynamics under cereals varied strongly according to aspects of
the respective cropping system, especially precrop and fertilization. Green manure but
also farmyard manure obviously increased short-term decomposable fractions of
SOM, promoting mineralization of SOM in the following period. Long-term changes of
SOM in the experiment were somewhat less pronounced than year-to-year changes,
pointing on the high importance of consideration of short-term SOM dynamics in
humus management
