1. National Engineering Lab. for Efficient, Utilization of Soil and Fertilizer Resources, National Engineering & Technology, Research Center for Slow and Controlled Release Fertilizers; College of Resources and Environment, Shandong Agricultural Univ.; Taian Shandong 271018 China
2. Dep. of Soil and Water Science, Tropical Research and Education Center; Univ. of Florida; Homestead FL 33031