1. Dep. of Agronomy and Horticulture Univ. of Nebraska 402 West State Farm Road North Platte NE 69101 USA
2. Agricultural Sciences and Production Environment Zamorano Pan‐American Agricultural School P.O. Box 93, km 30 Tegucigalpa Honduras
3. Dep. of Rural Engineering Sao Paulo State Univ. 3780 Universitaria Av. Botucatu SP 18610034 Brazil