Over the past few years, with funding from Ohio Soybean Council, we’ve re-examined Ohio’s soybean planting date, row width, and seeding rate recommendations. Here are some things to keep in mind, as we approach planting:
Soybean planting date has a large effect on yield. Yield reduction as a result of late planting ranges from 0.25 to 1 bushel/acre/day depending on row width, date of planting, and variety.
In southern Ohio, soybeans should be planted any time after April 15 when soil conditions are suitable. In northern Ohio, soybean planting can begin the last week of April if soil conditions are suitable.
Soybeans should not be planted until soil temperature reaches 50 degrees Fahrenheit and moisture is present at planting depth. Planting too early (when conditions are not adequate) comes with risk such as damping-off, bean leaf beetle, and late spring frosts.
In Ohio, most soybeans are grown in narrow rows: 7.5- or 15-inch row width. Soybeans grown in narrow rows generally produce more grain because they capture more sunlight energy, which drives photosynthesis. Row width should be narrow enough for the soybean canopy to close by flowering. With later planting dates, it is increasingly necessary to plant soybeans in narrow row widths to maximize yield.
The effect of plant population on yield is very small over the normal range of seeding rates and for any particular set of conditions. For a crop planted before May 20 in narrow rows, final populations of 100,000 to 120,000 plants/acre are generally adequate for maximum yield.
Final population is a function of seeding rate, quality of the planting operation, and seed germination percentage and depends on such things as soil moisture conditions, seed-soil contact, disease pressure, fungicide seed treatments, etc.
In our research trials, we planted 140,000-150,000 seeds/acre in 15-inch row width and achieved final stands ranging from 109,000-147,000 plants/acre with an average of 132,000 plants/acre. Our seeding rate research is on-going with variable seeding rate trials being conducted this year.