Soybean seed weights are lower this year due to drought, which means growers will need to calibrate their planters and estimate seed requirements differently, a University of Nebraska crops specialist said.

Soybean seeds from NU trials are weighting in at about 3,400 seeds per pound this year, said Roger Elmore, crops specialist. The last two years seeds weighed around 3,000 to 3,200 seeds per pound. Before the current drought, in 1998, seeds were at 2,500 seeds per pound.

Soybean seed weight is determined in August.

"If you have a hot, dry August, you'll have smaller seeds," he said. And it's worse the further east one goes.
"Some companies are talking 4,000 seeds per pound," Elmore said. "Since there isn't as much irrigation further east, the seeds get smaller."

However, since soybean seeds are sold by the pound, growers actually can save money this year by getting more seeds per pound. More seeds per pound can plant more acres. Since prices shouldn't be going up, soybean growers should be getting about 1,000 more seeds per pound than in wetter years, the Institute of Agriculture and Natural Resources specialist said.

However, this will require some extra caution when calibrating the planter this year. "If soybeans are planted too thick, farmers will waste seed," he said. "Growers can save a lot on seed costs, but need to estimate seed needs carefully."

To make sure seed isn't wasted this year, growers will need to look at the seed weight listed on the bag to calibrate their planters correctly. If not listed, contact the seed dealer to obtain seeds per pound for that specific lot number.

For example, at the pre-drought average of 2,500 seeds per pound, the normal seeding rate would be 60 pounds per acre, or about 150,000 seeds. However, a seed lot with 3,500 seeds per pound would have a planting rate of about 43 pounds per acre. That would be a 28 percent savings of seed costs relative to normal seed weights and a normal year, Elmore said. At today's seed prices, that would be equal to about a $9 per acre savings.
Also, in good soil conditions, smaller seeds will come up out of ground faster and there will be more root development.

However, it isn't all good news, Elmore said. Some researchers have found that if the soil crusts after a rain, there will be decreased emergence and decreased seedling and root weights. This means a poorer stand, increased weed control problems and possibly reduced yields.

For more information about soybean seeding rates, consult NU Cooperative Extension NebGuide G99-1395-A, Soybean Seeding Rates, available from a local Cooperative Extension office or on the Web at http://ianrpubs.unl.edu/fieldcrops/g1395.htm.