1. Univ. of Copenhagen; Dep. of Plant and Environmental Sciences; Thorvaldsensvej 40 Frederiksberg C Denmark
2. Sino-Danish Center for Education and Research (SDC)
3. Chinese Academy of Agricultural Sciences; Inst. of Agricultural Resources and Regional Planning; Key Laboratory of Plant Nutrition and Fertilizer/Ministry of Agriculture; 12 Zhongguancun Nan Lu, Haidian Beijing China