By planting at the optimum time and reducing seeding rate by 40 percent (137,500 to 82,500 seed per acre), growers would increase the soybean yield potential and save nearly $20 per acre in seed cost, and across South Carolina’s expected 550,000 to 570,000 acres in 2011, savings would be in the $10 million range.

Veteran North Carolina Soybean Specialist Jim Dunphy agrees with the reduction in seeding rate, with one significant concern — determinate versus indeterminate varieties.

Dunphy says, “Maturity Group III and Group IV beans have gained some popularity in recent years in the upper Southeast. The percentage of these soybean varieties grown is small, but a few growers have had good success with them.

“These indeterminate varieties are a little different animal than our more popular determinate varieties. We know what we will get with different seeding rates with most of the determinate varieties we plant in North Carolina — that’s not always the case with these Group III and IV beans,” he says.

Increasing seeding rate on these indeterminate varieties from 100,000 per acre to 150,000 per acre may produce a thicker, better looking plant, but yields will be about the same, he adds.

“Even to get high yields, in the 70 bushel per acre range, 50,000 seed per acre for determinate varieties and 100,000 seed per acre for indeterminate varieties planted in May is adequate. If you’re not getting a bushel and a half per pound of seed you plant, or 60 bushels from 40 pounds of seed, plant population is not what’s holding yields back,” Dunphy says.