1. Dep. of Crop, Forest and Environ. Sci.; Univ. of Basilicata; Viale Ateneo Lucano 10 85100 Potenza Italy
2. W.K. Kellogg Biological Station, Michigan State Univ.; Hickory Corner MI
3. Institute for Sustainable Resources, Queensland Univ. of Technology; Brisbane QLD Australia
4. Dep. of Agricultural & Biological Eng.; Univ. of Florida; Gainesville FL 32611
5. Natural Resource Ecology Lab., and Dep. of Soil and Crop Sciences; Colorado State Univ.; Fort Collins CO 80523-1499
6. Dep. of Crop and Soil Sciences; Michigan State Univ.; East Lansing MI 48824