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Soybeans [Glycine max (L.) Merr.] grown in the northern latitudes generally have lower protein concentrations than in the southern latitudes, reducing the value of northern grown soybeans. The objectives of this research were to: (i) study maturity zones within Minnesota for soybean seed yield, protein concentration, and oil concentration; (ii) compare performance of soybean varieties grown in producers' yield-contest fields with University of Minnesota research plots; and (iii) analyze seed yield, protein concentration, and oil concentration means and stability statistics for 30 soybean varieties. Yield, protein, and oil data were collected from University of Minnesota research trials across 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 concentration from southern to northern Minnesota, with higher yield and protein concentration among the same varieties grown in central Minnesota compared with northern Minnesota. Yields were highest in producers' yield-contest fields, but no protein and oil concentration differences were noted between yield-contest fields and research plots. Seed yield, protein concentration, and oil concentration means, as well as three stability statistics, differed among 30 varieties grown in 15 environments. The three stability statistics consisted of two nonparametric statistics based on variety ranks and Kang's yield-stability statistic. These results suggest that stability statistics, in addition to variety means, could be used by consultants, variety testing personnel, and breeders to recommend the most appropriate varieties for maximum yield and protein concentration. |
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