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Growth, Yield, and Yield Component Changes among Old and New Soybean Cultivars

Dep. of Agronomy, Iowa State Univ., 2104 Agronomy Hall, Ames, IA 50011-1010

View larger version (14K): [in this window] [in a new window]   Fig. 1. Total plant dry matter taken during the season at (a) De Witt, (b) Nevada, and (c) Whiting, 2005 to 2006. Each point is the average of two new soybean cyst nematode (SCN)-resistant (NR), two new SCN-susceptible (NS), and two old SCN-susceptible (OS) cultivars. Symbols *, **, *** indicate significant differences (P = 0.05, 0.01, and 0.001, respectively) and ns indicates no significant difference among new (N) and old (O) cultivars and NR and NS cultivars at the same sampling date.

View larger version (11K): [in this window] [in a new window]   Fig. 2. Leaf area index (LAI) taken between 42 and 105 days after emergence (DAE) at (a) De Witt, (b) Nevada, and (c) Whiting, 2005 to 2006. Each point is the average of two new soybean cyst nematode (SCN)-resistant (NR), two new SCN-susceptible (NS), and two old SCN-susceptible (OS) cultivars. Symbols *, **, *** indicate significant differences (P = 0.05, 0.01, and 0.001, respectively) and ns indicates no significant difference among new (N) and old (O) cultivars and NR and NS cultivars at the same sampling date.

View larger version (19K): [in this window] [in a new window]   Fig. 3. Relationship between crop growth rate and seeds m–2 for six cultivars grown at three locations in Iowa during 2005 and 2006. The model Seeds m–2 = cultivar + CGR + cultivar x CGR was evaluated in Proc Mixed to determine the relationship among CGR (R1–R5.5) and the number of seeds m–2. The cultivar x CGR interaction was not significant (P = 0.96) but the cultivar term was significant (P 0.001) indicating cultivar response models shared a common slope (b1 = 96.0) but different intercepts. Each point represents the mean of n = four observations.

View larger version (17K): [in this window] [in a new window]   Fig. 4. Leaf area index (LAI) 105 DAE and seeds m–2 for six soybean cultivars grown in Iowa at three locations during 2005 to 2006. The model seeds m–2 = cultivar + LAI + cultivar*LAI was evaluated in Proc Mixed to determine the relationship among LAI 105 DAE and the number of seeds m–2. The cultivar*LAI interaction was not significant (P = 0.44) but the cultivar term was significant (P 0.001) indicating that cultivar response models shared a common slope (b1 = 219) but different intercepts. Each point represents the mean of n = four observations.