1. State Key Lab. of Soil and Sustainable Agric.; Institute of Soil Science, Chinese Academy of Sciences; P.O. Box 821 Nanjing 210008 China
2. College of Resource and Environ.Science, Nanjing Agricultural University; Nanjing 210095 China
3. Institute of Soil, Water, and Environ. Sci., Agric. Research Organization; The Volcani Center; Bet Dagan 50250 Israel