Single- and three-way-cross hybrids, and differences in soil types and climate, have made single-environment testing of corn hybrids inapplicable for variety evaluation. Growers must test varieties under their own growing conditions before making selections.

The authors express their thanks to cooperating growers and seedsmen. Special thanks for protein determinations are expressed to James Quick, Technologist, Cooperative Extension Plant-Soil-Water Analysis Laboratory, and his staff.