1. Inst. of Soil Science and Soil Geography, Univ. of Bayreuth; D-95440 Bayreuth Germany
2. Natural Resources Conservation Service; 100 Centennial Mall North Lincoln NE 68516
3. USDA-ARS; Soil-Plant-Nutrient Research; 301 S. Howes St., P.O. Box E Fort Collins CO 80522-0470