1. Institute of Soil and Fertilizer, and Ministry of Agriculture Key Laboratory of Plant Nutrition and Nutrient Cycling, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
2. College of Natural Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China;
3. Research Center for Eco‐environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China;
4. Institute of Plant Nutrition (330), University of Hohenheim, D‐70593 Stuttgart, Germany