1. USDA-ARS Crop Systems and Global Change Lab; Bldg. 001, 10300 Baltimore Ave. Beltsville MD 20705
2. Dep. of Agricultural and Biological Engineering; Univ. of Illinois at Urbana-Champaign; 1304 W. Pennsylvania Ave. Urbana IL 61801
3. Dep. of Rural System Engineering; Research Institute for Agriculture and Life Sciences, Seoul National Univ.; San 56-1, Sillim-dong, Gwanak-gu Seoul 151-742 Republic of Korea
4. Dep. of Civil and Environmental Engineering; Hanyang Univ.; 17 Haengdang-dong, Seongdong-gu Seoul 133-791 Republic of Korea