1. Dep. of Soil Science; Univ. of Manitoba; 380 Ellis Bldg. Winnipeg Manitoba Canada R3T 2N2
2. North Central Soil Conservation Research Lab.; USDA-ARS; Morris MN 56267
3. South Dakota State Univ.; Dep. of Plant Science; 247 SNP, Box 2140C Brookings SD 57007-2141