Yield and agronomic responses of soybean to cotyledon and unifoliolate node removal

Field experiments were conducted over two years at two locations in Illinois to investigate the response of soybean [Glycine max (L.) Merr.] to simulated hail injury applied at the cotyledon (VC) stage. Removal of one or both cotyledons from all plants or of both cotyledons from alternating plants did not reduce mature plant height or yield in any environment. Cutting the stem off just below the unifoliolate node, alone or in conjunction with the removal of a single cotyledon, reduced yield by 11 to 21% in three of the four environments. It appears that soybean cotyledons are of little importance once the unifoliolate leaves have expanded.