Reproductive Abscission and Yield Response of Soybean to Root and Canopy Competition

Abstract

AbstractInterplant competition has been shown to influence plant architecture and seed yield. However, the influence of individual root or canopy competition on soybean [Glycine max (L.) Merr.] yield has not been identified. Field studies were conducted to determine the effects of root and canopy competition on abscission of reproductive structures and seed yield of the soybean cultivar Forrest. Plots were established on a Captina silt loam (fine‐silty mixed mesic Typic Fragiudults). Treatments were (i) no competition (ii) root competition only (iii) canopy competition only and (iv) both root and canopy (combined) competition. There was no difference among no, root, and canopy competition in the total number of reproductive structures produced and retained in 1985. However, in 1986 root and canopy competition resulted in an average of 281 and 166 reproductive structures produced and retained, respectively. In both years, combined competition caused the greatest reduction in the number of reproductive structures produced and retained. Combined competition resulted in 52 and 58% abscission in 1985 and 1986, respectively. In 1985, no, root, and canopy competition had similar effects on pod number per plant with an average of 387 pods, while combined competition resulted in only 99. In 1986, however, no competition resulted in the largest number of pods (310), combined competition resulted in the smallest number of pods (34), and root and canopy competition were intermediate with an average of 184 pods per plant. Subjecting plants to root competition decreased total seed weight and total seed number per plant by 44 and 42%, respectively, while canopy competition reduced total seed weight and number by 78%.