Editors Note: The following commentary is provided by Dr. Richard L. Cooper, USDA/ARS.
Variable rate technology (VRT), using lower seeding rates on the more productive soils to reduce lodging and increase yield, makes a lot of sense. However, seeding rate itself can become a yield-limiting factor.
You have to ask the question: What would the yields be in these high yield areas if I could use a higher seeding rate without lodging?
Semi-dwarf soybean varieties provide this opportunity. Based on many years of research, semi-dwarf varieties solid-seeded in 7- to10-inch row spacing at a seeding rate of 270 viable seeds/acre will maximize the yield on highly productive soils. Seventy to 80 bu/acre yields are not uncommon and in unusually favorable seasons (early warm spring conditions resulting in earlier flowering), 90 to 100 bu/acre yields have been obtained.
I encourage growers to consider changing varieties "on the go," planting the semi-dwarf varieties at 270,000 viable seeds/acre on the more productive soils and the taller, conventional varieties at 200,000 viable seeds/acre on the less productive soils. This is already possible with air drills that have two compartments in the seed cart. We need this same capability with conventional drills (e.g., two seed compartments and variable rate technology).
I am confident with grower ingenuity, such a machine can quickly be developed.
Dr. Richard L. Cooper; USDA/ARS
Ohio Ag Research and Development Center; Wooster, OH