The Physiological Basis of Soybean Yield Potential and Environmental Adaptation

The soybean [Glycine max (L.) Merr.] was introduced into North America in 1765 (Hymowitz and Harlan, 1983). For many years thereafter it was used as a forage crop. However, its value as an oilseed crop grew after the turn of the century and, by 1924, nearly 181,300 ha (25% of the total U.S. crop) were harvested for seed. After the 1940s, nearly 100% of the crop was harvested for seed. By the 1960s, its value as a source of protein began exceeding its value as a source of oil. Nearly 30 million hectares of U.S. soybeans were harvested for seed in 2001.