Professional positions held Sept. 1978 - Dec. 1986  Scientific co-worker at the plant protection office, State of Brandenburg, responsible for fruit orchards and tree nurseries. Jan. 1987 - March 1990 self-employed farmer (horticulture), March 1990 - Dec. 1991 Scientific co-worker at the Department Plant Growth of the Institute for Vegetable Production, Academy of Agricultural Science, Großbeeren, East Germany (DDR), Nov./Dec. 1991 Visiting scientist at the Federal Institute for Agriculture in the Alps, Gumpenstein, Austria, working group of M. Sobotik since Jan. 1992 Scientific co-worker at the Department of Plant Nutrition, Institute for Vegetable and Ornamental Crops, Großbeeren, Germany June - Sept. 1992 Visiting scientist at the Institute for Soil Fertility, Haren, The Netherlands (funded by the European Union), working group of M. van Noordwijk and M. Heinen July 1997 – July 1998 Visiting scientist at the Department of Crop and Soil Science of the University of Georgia, Griffin Campus, USA (funded by the German Ministry of Agriculture and the University of Georgia), working group of K.T. Ingram and M.I. van Iersel Sept./Oct. 1999 Visiting scientist at the Institute of Soils and Water, Agricultural Research Organisation-ARO, The Volcani Center, Bet Dagan, Israel (funded by the German Ministry of Agriculture and the ARO), working group of B. Bar Yosef August/September 2000. Visiting Scientist at the Department of Crop and Soil Science of the University of Georgia, Griffin Campus, USA (funded by the German Ministry of Agriculture and the University of Georgia), working group of K.T. Ingram since 2005. Lecturer for Plant Nutrition at the University of Applied Science Berlin