1. Dep. of Agric. Chemistry, Faculty of Agric.; Iwate Univ.; Morioka 020 Japan
2. Dep. Soil Science and Agric. Chemistry; Jilin Agric. Univ.; Changchun Jilin People's Republic of China
3. Dep. of Soil Science; Univ. of Saskatchewan; Saskatoon SK S7N 0W0 Canada