1. Institute of Crop Farming and Grassland Research, Section Crop Farming, University of Hohenheim, 70599 Stuttgart, Germany
2. Institute of Process Engineering, Federal Research Center for Nutrition and Food, location Karlsruhe, 76131 Karlsruhe, Germany
3. University of Hohenheim, Experimental Station Ihinger Hof, 71272 Renningen, Germany
4. Institute for Special Crop Cultivation and Crop Physiology, University of Hohenheim, 70593 Stuttgart, Germany