On-farm research with early maturing soybean varieties in Kentucky in both 1993 and 1994 has indicated that Maturity Group (MG) II varieties yield competitively with our traditional MG IV varieties. In those tests, four MG II varieties were compared with a single, high yielding MG IV variety (Asgrow A4715) over a range of planting dates on a total of 27 farms across both years. Asgrow A4715 averaged 43 bu/A, while the best MG II variety (Jack) averaged 39 bu/A. Such on-farm strip tests are valuable for comparing varieties under true production conditions. However, strip tests can effectively compare only a handful of the early maturing varieties available. In contrast, the soybean variety trials conducted by Iowa State University routinely include over 200 MG II varieties. In on-station tests at the UK Ag. Experiment Station during the same 2 years, where 12 MG II varieties were compared in four planting dates each year, the best variety averaged 10 bu/A more than the worst variety. However, since we were only able to compare 12 varieties in the on-station tests, both the on-farm and on-station tests could have easily missed some of the best MG II varieties.

An alternative which would increase the number of varieties being compared, would be to simply pick the best early maturing varieties from yield tests conducted in the northern locations in which MG II varieties are routinely tested. That strategy assumes that varieties which perform well in the north will continue to perform well when they are moved well south of their normal zone of production. Several soybean breeders, both public and private, have indicated that they feel that some varieties might move south better than others. Traits which have been cited as potentially advantageous for such a southerly move include: 1) taller plant height, 2) higher lodging scores in northern locations (indicating good vegetative growth potential), 3) warmer temperature tolerance, and 4) greater tolerance to pests (such as nematodes, insects, diseases, or weeds). The objective of this research was to compare Kentucky yield performance to northern Illinois yield performance of the same group of commercial and public MG II varieties.

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