1. Ministry of Agriculture Key Lab. of Plant Nutrition and Fertilizer Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences Beijing 100081 P.R. China
2. International Plant Nutrition Institute China Program Beijing 100081 P.R. China
3. Beijing Academy of Agriculture and Forestry Sciences, Beijing Engineering Technology Research Center for Slow/Controlled‐Release Fertilizer Institute of Plant Nutrition and Resources Beijing 100097 P.R. China
4. College of Resources and Environment Henan Agricultural Univ. Zhengzhou 450002 P.R. China
5. Hebei Academy of Agriculture and Forestry Sciences Institute of Agricultural Resources and Environment Shijiazhuang 050051 P.R. China
6. Shandong Academy of Agricultural Sciences Institute of Agricultural Resources and Environment Jinan 250100 P.R. China
7. Shanxi Academy of Agricultural Sciences Institute of Agricultural Resources and Environment Taiyuan 030031 P.R. China