At the height of the no-till drill craze in the 1990s it wasn't uncommon to hear of someone planting 225,000 to 250,000 soybean seeds per acre. Those were the days when seed companies were just beginning to urge farmers to seed by number of seed per acre, not pounds per acre. From variety to variety and year to year, numbers of seeds per pound in soybeans can vary widely.
Today more farmers are in 15-inch row with split-row planters, while some still drill and others have moved back to 30-inch rows or other combinations. That may explain part of the reason for lower seeding rates.
Shaun Casteel, Purdue University Extension soybean specialist, has been doing tests over the past three or four years that indicate that soybean seeding rates don't probably need to be as high as those that many people use. Even some seed companies are urging use of good practices and reduction in seeding rate.
A survey of nearly 70 Master Farmers who have received the Master Farmer award at some point in the past tend to bear out these indications. The respondents were asked how many soybeans per acre they planted, and were given ranges.
Surprisingly, one in 10 aim to plant 80,000 to 120,000 seeds per acre. There is ample evidence showing 80,000 plants per acre may be sufficient if the factors cooperate, but few people intentionally plant at that level from the start. Germination is seldom 100%.
Eight of 10 are planting between 120,000 and 180,000 seeds per acre. As you break that down, 37% said they plant 120,000 to 150,000 seeds per acre, and 44% are planting 150,000 to 180,000 seeds per acre.
About 10% still say they're planting above 180,000 seeds per acre, somewhere form 180,000 to 210,000 seeds per acre. No one says they are intending to plant more than 210,000 seeds per acre. That's a definite shift over the past two decades if that's accurate.