Influence of Soybean (Glycine max)Planting Date on Velvetleaf (Abutilon theophrasti)Competition

Abstract

A 2-yr study was conducted to determine the influence of early and late soybean [Glycine max(L.) Merr.] planting dates on the competitiveness of velvetleaf (Abutilon theophrastiMedic). Velvetleaf was planted at densities of one plant per 61 and 30 cm of row, and competition ranged from 4 weeks to full season. Soybean planting dates were mid-May and late-June. Velvetleaf emerging with soybeans in mid-May were twice as competitive as those emerging with soybeans planted in late-June. A density of one velvetleaf per 30 cm of row competing full season reduced soybean yields 27% for the early and only 14% for the late planting date. The competitive difference was due to the short-day photoperiodic response of velvetleaf. Although the early growth stages of soybeans are more competitive than those of velvetleaf, 10 weeks after emergence velvetleaf competition reduced soybean growth and development. Velvetleaf does not appear to be a potential major problem in Arkansas for soybeans planted in June due to its photoperiodic response and late season competitiveness. However, the weed could present problems for soybeans planted early, especially when an early maturing variety is used.