AGRONOMIC PERFORMANCE AND STABILITY OF SOYBEAN VARIETIES GROWN IN 3 MATURITY ZONES OF MINNESOTA

Soybeans [Glycine max CL.) Merr.] grown in the northern latitudes gene rally have lower protein concentrations than in the southern latitudes , reducing the value of northern grown soybeans. The objectives of thi s research were to: (i) study maturity zones within Minnesota for soyb ean seed yield, protein concentration, and oil concentration; (ii) com pare performance of soybean varieties grown in producers' yield-contes t fields with University of Minnesota research plots; and (iii) analyz e seed yield, protein concentration, and oil concentration means and s tability statistics for 30 soybean varieties. Yield, protein, and oil data were collected from University of Minnesota research trials acros s 15 environments from 1991 to 1995. Producer data were collected from the Minnesota Soybean Grower's Association Yield Contest from 1991 to 1995. The general trend was a decrease in yield and protein concentra tion from southern to northern Minnesota, with higher yield and protei n concentration among the same varieties grown in central Minnesota co mpared with northern Minnesota. Yields were highest in producers' yiel d-contest fields, but no protein and oil concentration differences wer e noted between yield-contest fields and research plots. Seed yield, p rotein concentration, and oil concentration means, as well as three st ability statistics, differed among 30 varieties grown in 15 environmen ts. The three stability statistics consisted of two nonparametric stat istics based on variety ranks and Kang's yield-stability statistic. Th ese results suggest that stability statistics, in addition to variety means, could be used by consultants, variety testing personnel, and br eeders to recommend the most appropriate varieties for maximum yield a nd protein concentration.