Comparative Performance of Semideterminate and Indeterminate Soybean Lines1

Abstract

Forty semideterminate and 40 indeterminate soybean [Glycine max (L.) Merr.] lines from each of three crosses were evaluated in 0.5‐ and 1.0‐m row spacings for 2 years at Lafayette, Ind. The objectives of the study were to compare the agronomic characteristics of the two plant types and to determine if the plant types responded differently to row spacings.Yields of the 0.5‐m rows averaged 13% higher than those of the 1.0‐m rows in the 2 years of the study. This response was due primarily to increased yields in the 2nd year of the test.The indeterminate progenies were an average 5% higher in seed yield, 1 day later in maturity, and 12 cm taller than the semideterminate progenies. Interactions of plant type ✕ row spacing were not significant for any characteristic evaluated except maturity in one cross. These data indicated that both the semideterminate and indeterminate lines responded similarly to the two row spacings used in this study.Regression of seed yield on plant height for the two plant types showed similar regression coefficients in most of the comparisons, indicating that the increases in seed yield associated with increased plant height were similar for the two plant types. Only half the regression coefficients were significant for lodging scores regressed on plant height for the two plant types. Significant coefficients were similar for the two plant types, indicating that neither plant type resulted in superior lodging resistance. The data indicated that among soybeans adapted to the Midwest, either plant type could be used successfully in a soybean improvement program.