Permanent-soil monitoring sites for documentation of soil-fertility development after changing from conventional to organic farming

For monitoring soil fertility after changing farm management from highly conventional to organic farming on the newly established research farm of Kassel University, two permanent-soil monitoring sites were installed in 1999. Representative locations for installing the permanent-soil monitoring sites were selected using geographical information systems (GIS), based on available data from geology, topography, soil taxation, land use, and intensive auger-borehole records and analysis with a very high spatial resolution of data. The soils are represented by a Luvisol derived from loess and a Vertisol developed from claystone. The soil properties of the two monitoring sites measured immediately after changing to organic farming showed high contents of extractable nutrients as a result of the former intensive fertilization practice during conventional farm management. The microbial soil properties of the two monitoring sites were in the medium range of regional soils. A first evaluation of the development of soil properties was done after 5 y of monitoring. The soil organic-matter content increased slightly after grass-clover and after application of farmyard manure. The amounts of K and P decreased clearly at the loess site without application of farmyard manure. At the clay site, the unique application of farmyard manure led to increasing contents of extractable K and P in the top soil. The variation of soil properties increased clearly after perennial crops like grass-clover and in years after application of farmyard manure.