Row Width and Seeding Rate Performance of Indeterminate, Semideterminate, and Determinate Soybean
1991
Ablett, G. R. | Beversdorf, W. D. | Dirks, V. A.
In the northern-soybean [Glycine max. (L.) Merr.]-producing areas of the USA and Canada, indeterminate (IND) soybean cultivars predominate. Over the last several years, soybean cultivars with semideterminate (SDT) or determinate (DET) stem termination type have been developed, however, basic agronomic information is limited for these types in the Maturity Group I to II soybean growing areas of southern Ontario. For this study, six cultivars (two per stem type) were seeded at 10-, 20-, and 30-in.-row widths and 160 000, 240 000 and 320 000 seeds/acre seeding rates in 1983,1984, and 1985. Yield increased when row width decreased from 30 in. to 10 in. on average, 14, 20, and 23% for the IND, SDT, and DET stem type, respectively. These results indicate a disadvantage for wide row production for all three stem termination types, although differences between cultivars within a stem type were not consistent each year. Seeding rate had no effect on yield of the IND stem type, or on yield of the SDT stem type in either 1984 or 1985. Yield, however, was reduced for the SDT stem type in 1983 when seeding rates were increased above 160 000 seeds/acre. Optimal yields for the DET stem type occurred at 240 000 seeds/acre. Plant height varied only with the year and cultivar. The SDT and DET cultivars were more lodging resistant than the IND cultivar Harcor each year, but did not differ from the other IND cultivar, Premier. The overall results suggest that although all stem types were capable of producing high yields, less flexibility exists in southern Ontario in choice of both row width and seeding rate for Maturity Group II cultivars with either a DET and SDT stem type than with cultivars having the IND stem type.
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