Effect of Stem Termination on Soybean Traits in Southern U.S. Production Systems

Southern U.S. soybean [ Glycine max (L.) Merr.] are primarily determinate and are grown in a diverse array of environments. Understanding the yield response of different plant types to southern environments may lead to improved yield. Our objective was to determine if varying stem termination could increase yield in some environments. Eleven pairs of isolines varying for determinate and indeterminate growth habit were derived from two crosses. All lines and controls were grown at two locations for 2 yr, planted in May and June and with or without irrigation. Seven pairs were grown for a third year. Yield, height, lodging, and maturity data were collected. In all crosses and production systems, determinate lines were shorter, earlier maturing, and had less lodging than indeterminate lines. Yields of determinate and indeterminate lines were equal in all irrigation–planting date combinations. There was a trend for determinate lines to yield better than indeterminate lines with early planting and irrigation. The yield difference between growth habits was conditioned primarily by a complex interaction of random genetic and environment effects. The indeterminate growth habit may confer a yield advantage over the determinate growth habit in environments with limited yield and growth potential. This was due to the lower yield response to increasing environment productivity of indeterminate vs. determinate lines. Perhaps 10 to 15% of southern production environments have conditions where indeterminate types may yield better than determinate types. The yield advantage of indeterminate types in such environments appears small. The success of deploying indeterminate cultivars to low‐yield, low‐growth southern environments to maximize yield will depend on accurately predicting where these environments will occur.