A primary limiting factor for Iowa farmers chasing 100-bushel soybean yields is one that they have little control over — too much cloud cover, says Sotirios Archontoulis, an Iowa State University assistant professor of integrated cropping systems.

Cloud cover blocks solar radiation, which drives biomass production in soybeans, Archontoulis said last week at the Iowa Soybean Association Research Conference. Greater biomass production boosts soybean yield potential.

"One hour of daylight (at key growing stages) can greatly affect yield," said Archontoulis, who studied the production techniques Missouri farmer Kip Cullers used to grow...