Impact of Defoliation on Herbage and Seed Production of Strophostyles helvula and S. leiosperma

Trailing wild bean (Strophostyles helvula (L.) Ell. [Fabaceae]) yielded up to 1793 g herbage/plant/y (3.9 lb) and out-produced smooth-seeded wild bean (Strophostyles leiosperma (Torr. & Gray) Piper) by a factor of 1.8 to 3.4, depending on location and growing conditions. In contrast to trailing wild bean that appeared to be photoperiod sensitive and produced most of its seeds in autumn (63 g/plant/y [2.2 oz]) at the best site, smooth-seeded wild bean responded to light defoliation by increasing seed yields during the growing season (from 12 to 86 g/plant/y [0.4 to 3.0 oz]). Herbage fiber concentration decreased and crude protein increased when defoliation occurred throughout the growing season. Results suggest these Strophostyles species are suitable candidates for rangeland reseeding, wildlife feed, and prairie restoration in the southern Great Plains region.