Evaluation of Soybean Varieties for Certified Organic Production Neely-Kinyon Trial, 2003

Materials and Methods Varieties selected for the 2003 organic soybean variety trial included the following: IA3011, IA3021, IA3022, Pioneer 9305, Schillinger 240F.Y, and Schillinger 290F.HP. Plots measuring 20 × 40 feet were laid out in a completely randomized block design with four replications of each variety. Soybeans were planted at a depth of 2 inches on May 28, 2003, at a rate of 200,000 seeds/acre. Weed control was established through the following procedures: rotary hoe on June 6, 9, and 12; and cultivation on June 23, July 2, and July 14. Plant stands were counted on June 19, 2003. Bean leaf beetle sampling occurred on July 19, by sweeping across plants in each plot with a 15 in.-diameter sweep net. Insects were placed in Zip-lock bags and transported in coolers to Iowa State University. Insects were frozen until enumeration in the laboratory. Soybeans were harvested on October 9. The percentage of stained soybeans was determined by counting the number of stained soybeans in a 200-gram sample that was randomly collected from the harvest of each plot. Results and Discussion On June 19, stands in the Schillinger 290F.HP plots were significantly greater than in the IA3011 and IA3022 plots (Table 1). Grass weeds were significantly greater in IA3022 plots compared with all other varieties, but there was no significant difference in broadleaf weed number (Table 1). Yields in the IA varieties (IA3011, IA3021, and IA3022) were significantly greater than the Schillinger 290F.HP variety, averaging 36 bushels/acre. Bean leaf beetle populations were reduced in 2003, and on July 19, no beetles were found in IA3022, compared with an average of 2 beetles per 8 sweeps in the other varieties (Table 2). There was a trend toward lower seed staining in the Schillinger varieties, but because of low bean leaf beetle populations and low seed staining (average of 2.5%), there was no significant difference between varieties in overall seed staining in 2003 (Table 2).