Studies were conducted to evaluate density-dependent effects of tropic croton on weed and peanut growth and peanut yield. Tropic croton remained taller than peanut throughout the growing season, yet tropic croton density did not affect peanut or tropic croton heights. Tropic croton biomass per plant decreased linearly with increasing plant density. Peanut pod weight decreased linearly 4.7 kg/ha with each gram of increase in tropic croton biomass per meter of crop row. The rectangular hyperbola model was used to describe effects of tropic croton density on percent peanut yield loss. Estimated coefficients for a (maximum yield loss) and i (yield loss per unit density as density approaches zero) were 81 and 26 in 1988, 41 and 33 in 1989, and 33 and 61 in 1998, respectively. Although a and i values varied between years, yield loss predictions were stable between years at weed densities below two plants per meter of crop row. Even though the results show that tropic croton is less competitive than many broadleaf weeds in peanut, it has potential to substantially reduce yields and subsequently reduce economic return.
Nomenclature: Tropic croton, Croton glandulosus var. septentrionalis Muell.-Arg. #3 CVNGS; peanut, Arachis hypogaea L. ‘NC 10C’, ‘Florigiant’.
Additional index words: Competition, economic threshold, models, plant height, weed biomass, weed density.
Abbreviations: PRE, preemergence.