1. Division Urban Plant Ecophysiology, Faculty of Life Sciences, Albrecht Daniel Thaer‐Institute of Agricultural and Horticultural Sciences Humboldt‐University of Berlin Berlin Germany
2. Institute of Soil Science and Plant Nutrition Hochschule Geisenheim University Geisenheim Germany
3. Department of Plant Soil & Microbial Sciences Michigan State University East Lansing Michigan USA
4. Consultant for Organic Gardening Berlin Germany
5. Department of Plant Sciences University of Oxford Oxford UK