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Hemp sesbania interference in drill-seeded glyphosate-resistant soybean

Author:
Norsworthy, Jason K., Oliver, Lawrence R.
Source:
Weed science 2002 v.50 no.1 pp. 34-41
ISSN:
0043-1745
Subject:
Glycine max, Sesbania exaltata, buried seeds, developmental stages, field experimentation, glyphosate, hemp, herbicide resistance, planting, seed yield, sowing, soybeans, weed control, weeds, Arkansas
Abstract:
Field experiments were conducted at Fayetteville, AR, in 1997, 1998, and 1999 to evaluate the degree of interspecific interference between drill-seeded, glyphosate-resistant soybean and hemp sesbania as influenced by soybean population, hemp sesbania density, and a single glyphosate application. Soybean was planted at 247,000, 430,000, and 618,000 seed ha⁻⁻¹ with early-season emergence of 217,000, 371,000, and 521,000 plants ha⁻⁻¹. Hemp sesbania densities were 0, 4, 10, and 16 plants m⁻⁻² in combination with 0 and 1.12 kg ai ha⁻⁻¹ glyphosate applied at the V4 to V6 soybean growth stage. Untreated hemp sesbania produced a maximum of 49 million seed ha⁻⁻¹ with 217,000 soybean ha⁻⁻¹, whereas seed production of glyphosate-treated hemp sesbania ranged from 2.8 to 0.6 million seed ha⁻⁻¹ with 217,000 and 521,000 soybean ha⁻⁻¹, respectively. Soybean seed yield was reduced 43%% by 16 untreated hemp sesbania m⁻⁻², while glyphosate-treated hemp sesbania did not reduce seed yield. Averaged over all untreated hemp sesbania densities, soybean yield loss was reduced from 44 to 22%% by increasing the soybean population from 217,000 to 521,000 plants ha⁻⁻¹. Because of the absence of soybean yield loss at 521,000 soybean ha⁻⁻¹, this density appears beneficial when using a single application of glyphosate to provide season-long weed control. However, a single glyphosate application in combination with a high soybean density did not completely prevent hemp sesbania seed production, and the seeding rate required to achieve a stand of 521,000 plants ha⁻⁻¹ would not be affordable; thus, alternate management methods targeting hemp sesbania must be employed to prevent an increase in the number of seed in the soil seedbank and to prevent a potential shift in the weed spectrum.Nomenclature: Glyphosate; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A.W.Hill SEBEX; soybean, Glycine max L.
Agid:
1309202