Soybean seed costs have risen to the point at which farmers don’t want to plant more seeds than they need for top yields, according to University of Illinois crop sciences professor Emerson Nafziger.

With less costly soybean seed and the wide range of which soybean plant populations produce similar yields, soybean seeding rates have not historically been as closely calculated as those for corn.

High soybean yields are possible with a wide range of plant populations because single plants of most varieties will utilize a 7- to 9-inch area in all directions around the main stem. Plants adjust ...