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|Title:||Interference of Common Cocklebur (Xanthium Strumarium L.) and Velvetleaf (Abutilon Theophrasti Medic.) With Soybean Stands at Different Densities and Planting Patterns|
|Author(s):||Marwat, Khan Bahadar|
|Doctoral Committee Chair(s):||Nafziger, Emerson D.|
|Department / Program:||Agronomy|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Reduced stands of soybean and weed infestation is a common problem in soybean growing areas. The object of this study was to study the interference of common cocklebur (Xanthium strumarium L.) and velvetleaf (Abutilon theophrasti Medic.) with soybean stands of different densities and planting patterns. Field experiments were conducted during 1986 and 1987 at Urbana, Illinois. A randomized complete block design with 3 x 7 split-plot arrangements, having four replications was used. Weed treatments assigned to the main plots were: weed-free; common cocklebur; and velvetleaf. And seven subplots were soybean stands: control (26.22 plants/m row), and three levels of reduction, 20%, 40% and 60%, respectively, of the full stand, each arranged in two patterns: even and gapped. Weeds were planted in a diamond pattern at an interval of 1.5 m in the soybean rows at the time of soybean planting.
Soybean yield reduction by cocklebur and velvetleaf was 803 (25%) and 664 kg/ha (21%) compared to weed-free, respectively, averaged over stands and planting patterns. Yield decreased with stand reduction in both planting patterns, however, yield reductions were more severe in gapped compared to even stands. Seed weight was not significantly affected by stands and/or weeds while averaged for two years. Seed number/plant increased with stand reduction and decreased with weed interference. Soybean lodging decreased with stand reduction and increased with weeds interference, with cocklebur causing more lodging than velvetleaf. Percent light interception and basal pod height decreased with stand reduction; the pattern of decrease was quadratic in both the planting patterns. With cocklebur and velvetleaf present, canopies intercepted about 5% and 6% more light, respectively, compared to weed-free stands. Weed dry weight increased with stand reduction, with cocklebur accumulating more dry weight compared to velvetleaf. Interference from cocklebur with soybeans appeared to be primarily for resources other than light, while velvetleaf interference was accounted for mainly by light and/or allelopathy. In reduced stands of soybean, cocklebur was more competitive than velvetleaf, while in full stands velvetleaf caused yield reductions equal to or greater than those caused by cocklebur; however, the overall yield reductions caused by both weeds were not statistically different.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
|Date Available in IDEALS:||2014-12-16|