Common Ragweed (Ambrosia artemisiifolia) Interference in Soybeans (Glycine max)

Abstract

The influence of common ragweed (Ambrosia artemisiifoliaL.) interference on soybean [Glycine max(L.) Merr. ‘Ransom’] yield was studied in the field utilizing naturally occurring weed populations. The damage-threshold population for a full-season, in-row common ragweed infestation was four weeds/10 m of row, which resulted in an 8% yield loss. Soybeans kept weed-free for 2 weeks or longer after emergence in a dry year produced normal yields, but 4 weeks of weed-free maintenance was required when adequate moisture was available early in the growing season. Soybean yield was not reduced by a natural population of common ragweed if the period of interference was limited to 6 weeks or less after crop emergence. By 8 weeks after emergence, common ragweed height averaged 25 cm taller than soybeans, and the weed canopy intercepted 24% of the photosynthetically active radiation.