Growth Analysis of Soybeans (Glycine max) in Competition with Velvetleaf (Abutilon theophrasti)

Abstract

Field experiments were conducted to study the effects of varying velvetleaf (Abutilon theophrastiMedic.) densities and planting dates on the growth and yield of soybeans [Glycine max(L.) Merr. ‘Amsoy 71’]. Velvetleaf densities ranging from 2.5 to 40 plants/m2caused reductions in the dry weight of soybean leaves, stems, roots, and pods and seeds, and in the leaf area index, pod number, and seed yield when velvetleaf and soybean plants emerged at the same time. The magnitude of reduction in soybean growth and the time at which the reduction was first observed was dependent on weed density. Soybean growth reductions caused by high velvetleaf densities were less when conditions of high soil moisture content minimized the effects of competition for water. Velvetleaf emerging 21 and 23 days after soybean emergence did not reduce crop growth or yield.

Effects of simulated insect defoliation and annual weed competition on soybean and velvetleaf development

“…Staniforth (1965) determined that yields were depressed 31% when 3 velvetleaf/ 30 cm of row remained for the entire growing season. Hagood et al (1980) also confirmed that increasing velvetleaf densities would cause greater soybean yield losses. Full-season densities of only 2.5 velvetleaf/m^ of soil surface (randomly located weeds) caused significant yield reduc tions (26%).…”

“…Increasing full-season morningglory densi ties to 1 weed/15 cm of row resulted in soybean LAI reductions of 60%. Hagood et al (1980) reported that soybeans competing with 10 velvetleaf/ of soil surface displayed an LAI of 3.5 to 3.9 by 11 or 12 weeks after emergence. In contrast, weed-free soybeans possessed an LAI of 6.3 to 6.6 after the same interval had passed.…”

“…Weed competition also can limit soybean dry matter production. Hagood et al (1980) reported leaf, stem, root, and reproductive component reduc tions when soybeans from weedy (velvetleaf) plots were compared with weedfree soybeans. Higher weed densities resulted in an earlier detection of significant differences and a greater magnitude of difference.…”

“…Glycine max (Merr. ), has become available through information published since the inception of this project (Hagood et al, 1980;Hammond et al, 1979a;Hammond and Pedigo, 1982;Oliver, 1979), no published information on the effects of combinations of these pests is yet available.…”

Phytotoxic Exudates From Velvetleaf (Abutilon Theophrasti) Glandular Trichomes

“…The malvaceous weed, velvetleaf, interferes with the growth of several crops including com (Zea mays L.) (DeFelice, Witt and Slack 1984), cotton (Gossypium hirsutum L.) (Chandler, 1977) and soybeans [Glycine max (L.) Merr.] (Eaton, Russ and Feltner, 1976;Hagood et al, 1980;Dekker and Meggitt, 1983). Several investigators have attributed this interference to competition for water (Hagood et al, 1980;Dekker and Meggitt, 1983), light (Stoller and Woolley, 1985), and nutrients (Oliver, 1979), while others have implicated allelopathy (Colton and Einhellig, 1980;Bhowmick and Doll, 1982).…”