1. Dep. of Renewable Resources, 751 General Services Building; Univ. of Alberta; Edmonton AB T6G 2H1 Canada
2. V. P. Research Office; 3rd Floor University Hall, Univ. of Alberta Edmonton AB T6G 2J9 Canada
3. Dep. of Soil Science, 51 Campus Drive; Univ. of Saskatchewan; Saskatoon SK S7N 5A8 Canada