Palmer Amaranth (Amaranthus palmeri) Interference in Soybeans (Glycine max)

A 2-yr field study was conducted at Fayetteville, AR, to determine the effect of Palmer amaranth interference on soybean growth and yield. Palmer amaranth density had little effect on soybean height, but soybean canopy width ranged from 77 cm in the weed-free check to 35 cm in plots with 10 plants m–1of row 12 wk after emergence. Soybean yield reduction was highly correlated to Palmer amaranth biomass at 8 wk after emergence and maturity, soybean biomass at 8 wk after emergence, and Palmer amaranth density. Soybean yield reduction was 17, 27, 32, 48, 64, and 68%, respectively, for Palmer amaranth densities of 033, 0.66, 1, 2, 333, and 10 plants m–1of row. Soybean yield reduction and Palmer amaranth biomass were linear to approximately 2 Palmer amaranth m–1of row, suggesting intraspecific interference between adjacent Palmer amaranth is initiated at Palmer amaranth densities between 2 and 3.33 plants m–1of row.

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Effects of Palmer Amaranth (Amaranthus palmeri) Establishment Time and Distance from the Crop Row on Biological and Phenological Characteristics of the Weed: Implications on Soybean Yield

Weed Science ◽

10.1017/wsc.2018.84 ◽

2019 ◽

Vol 67 (1) ◽

pp. 126-135 ◽

Cited By ~ 8

Author(s):

Nicholas E. Korres ◽

Jason K. Norsworthy ◽

Andy Mauromoustakos

Keyword(s):

Seed Production ◽

Weed Management ◽

Cropping Systems ◽

Management Strategies ◽

Palmer Amaranth ◽

Yield Reduction ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Management Measures ◽

Weed Population Dynamics

AbstractInformation about weed biology and weed population dynamics is critical for the development of efficient weed management programs. A field experiment was conducted in Fayetteville, AR, during 2014 and 2015 to examine the effects of Palmer amaranth (Amaranthus palmeriS. Watson) establishment time in relation to soybean [Glycine max(L.) Merr.] emergence and the effects ofA. palmeridistance from the soybean row on the weed’s height, biomass, seed production, and flowering time and on soybean yield. The establishment time factor, in weeks after crop emergence (WAE), was composed of six treatment levels (0, 1, 2, 4, 6, and 8 WAE), whereas the distance from the crop consisted of three treatment levels (0, 24, and 48 cm). Differences inA. palmeribiomass and seed production averaged across distance from the crop were found at 0 and 1 WAE in both years. Establishment time had a significant effect onA. palmeriseed production through greater biomass production and height increases at earlier dates.Amaranthus palmerithat was established with the crop (0 WAE) overtopped soybean at about 7 and 10 WAE in 2014 and 2015, respectively. Distance from the crop affectedA. palmeriheight, biomass, and seed production. The greater the distance from the crop, the higherA. palmeriheight, biomass, and seed production at 0 and 1 WAE compared with other dates (i.e., 2, 4, 6, and 8 WAE).Amaranthus palmeriestablishment time had a significant impact on soybean yield, but distance from the crop did not. The earlierA. palmeriinterfered with soybean (0 and 1 WAE), the greater the crop yield reduction; after that period no significant yield reductions were recorded compared with the rest of the weed establishment times. Knowledge ofA. palmeriresponse, especially at early stages of its life cycle, is important for designing efficient weed management strategies and cropping systems that can enhance crop competitiveness. Control ofA. palmeriwithin the first week after crop emergence or reduced distance between crop and weed are important factors for an effective implementation of weed management measures againstA. palmeriand reduced soybean yield losses due to weed interference.

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Field Competition between Ivyleaf Morningglory (Ipomea hederacea) and Soybeans (Glycine max)

Weed Science ◽

10.1017/s0043174500059142 ◽

1984 ◽

Vol 32 (3) ◽

pp. 364-370 ◽

Cited By ~ 29

Author(s):

Ronald C. Cordes ◽

Thomas T. Bauman

Keyword(s):

Soil Moisture ◽

Glycine Max ◽

Leaf Area Index ◽

Leaf Area ◽

Dry Weight ◽

Growth And Yield ◽

Yield Reduction ◽

Area Index ◽

Soybean Yield ◽

Competition Effects

Detrimental effects on growth and yield of soybeans [Glycine max(L.) Merr. ‘Amsoy 77′] from density and duration of competition by ivyleaf morningglory [Ipomea hederacea(L.) Jacq. ♯3IPOHE] was evaluated in 1981 and 1982 near West Lafayette, IN. Ivyleaf morningglory was planted at densities of 1 plant per 90, 60, 30, and 15 cm of row in 1981 and 1 plant per 60, 30, 15, and 7.5 cm of row in 1982. Each density of ivyleaf morningglory competed for 22 to 46 days after emergence and the full season in 1981, and for 29 to 60 days after emergence and the full season in 1982. The best indicators of competition effects were leaf area index, plant dry weight, and yield of soybeans. Ivyleaf morningglory was more competitive during the reproductive stage of soybean growth. Photosynthetic irradiance and soil moisture measurements indicated that ivyleaf morningglory does not effectively compete for light or soil moisture. All densities of ivyleaf morningglory could compete with soybeans for 46 and 60 days after emergence in 1981 and 1982, respectively, without reducing soybean yield. Full-season competition from densities of 1 ivyleaf morningglory plant per 15 cm of row significantly reduced soybean yield by 36% in 1981 and 13% in 1982. The magnitude of soybean growth and yield reduction caused by a given density of ivyleaf morningglory was greater when warm, early season temperatures favored rapid weed development.

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Interference of Selected Palmer Amaranth (Amaranthus palmeri) Biotypes in Soybean (Glycine max)

International Journal of Agronomy ◽

10.1155/2012/168267 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Aman Chandi ◽

David L. Jordan ◽

Alan C. York ◽

Susana R. Milla-Lewis ◽

James D. Burton ◽

...

Keyword(s):

Glycine Max ◽

Acetolactate Synthase ◽

Dry Weight ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Fresh Weight ◽

Row Crops ◽

Soybean Yield ◽

Competitive Disadvantage

Palmer amaranth (Amaranthus palmeriS. Wats.) has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max(L.) Merr.] for 40 days after emergence by three glyphosate-resistant (GR) and three glyphosate-susceptible (GS) Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance.

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Interference of Wild Poinsettia (Euphorbia heterophylla) with Soybean (Glycine max)

Weed Technology ◽

10.1017/s0890037x00028517 ◽

1994 ◽

Vol 8 (4) ◽

pp. 679-683 ◽

Cited By ~ 7

Author(s):

Teresa S. Willard ◽

James L. Griffin ◽

Daniel B. Reynolds ◽

Arnold M. Saxton

Keyword(s):

Glycine Max ◽

Dry Weight ◽

Growing Season ◽

Field Studies ◽

Yield Reduction ◽

Soybean Yield ◽

Weed Interference ◽

Soybean Canopy ◽

Area Of Influence

Field-studies were conducted over two years to determine the area of influence and duration of interference of wild poinsettia in soybean. Soybean canopy width averaged across years was reduced approximately 10% beginning at 6 wk of interference for both the 0- to 10-and 10-to 20-cm distances from the weed. Soybean dry weights decreased from 14 to 38% within 20 cm of the weed for 12 through 18 wk of interference. In 1990, soybean yield within 10 cm of wild poinsettia was similar to distances of 10 to 20 and 20 to 40 cm, but was less than that for distances greater than 40 cm from the weed. Weed interference resulted in a 9.5% yield reduction in the 0- to 10-cm distance when compared with the 80-to 100-cm distance. In contrast, yield of soybean in 1991 growing within 10 cm of the weed was less than at greater distances, corresponding to an 18% yield reduction when compared with 80 to 100 cm. Differences in wild poinsettia dry weights when growing alone and when growing within the soybean row occurred after 6 and 8 wk of interference in 1990 and 1991, respectively. In 1991 when rainfall during the growing season was twice that of the previous year, canopy width and dry weight of wild poinsettia growing within the soybean row were reduced an average of 57 and 82%, respectively, compared with weeds growing alone.

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Influence of Soybean (Glycine max) Population and Herbicide Program on Palmer Amaranth (Amaranthus palmeri) Control, Soybean Yield, and Economic Return

ISRN Agronomy ◽

10.5402/2012/947395 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8

Author(s):

Amy E. Hoffner ◽

David L. Jordan ◽

Alan C. York ◽

E. James Dunphy ◽

Wesley J. Everman

Keyword(s):

North Carolina ◽

Glycine Max ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Production Costs ◽

Soybean Plant ◽

Amaranthus Palmeri ◽

Economic Return ◽

Soybean Yield ◽

Herbicide Resistant

Palmer amaranth (Amaranthus palmeri S. Wats) has become one of the most prominent and difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. A survey was conducted in North Carolina during fall 2010 to estimate the magnitude of this problem. Palmer amaranth was present in 39% of 2,512 fields representing 0.24% of soybean ha in North Carolina. In recent years, growers have reduced soybean seeding rates in an effort to decrease production costs associated with technology fees. However, given the increase in prevalence of Palmer amaranth and the difficultly in controlling this weed due to herbicide resistance, growers may need to reconsider reductions in seeding rates. Therefore, research was conducted during 2010 and 2011 to determine if Palmer amaranth control, soybean yield, and economic return were affected by soybean plant population, preemergence (PRE) and postemergence (POST) herbicides, and herbicide resistant traits (glufosinate-resistant and glyphosate-resistant cultivars). Applying PRE or POST herbicides and increasing soybean population increased Palmer amaranth control, soybean yield, and economic return when compared with POST herbicides only or when lower soybean populations were present. Efficacy of glufosinate and glyphosate did not vary in most instances, most likely because these herbicides were applied timely, and the frequency of glyphosate resistance did not exceed 10% in these fields.

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Management of Palmer Amaranth (Amaranthus palmeri) in Glufosinate-Resistant Soybean (Glycine max) with Sequential Applications of Herbicides

ISRN Agronomy ◽

10.5402/2012/131650 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Amy E. Hoffner ◽

David L. Jordan ◽

Aman Chandi ◽

Alan C. York ◽

E. James Dunphy ◽

...

Keyword(s):

North Carolina ◽

Glycine Max ◽

Plant Population ◽

Palmer Amaranth ◽

Soybean Plant ◽

Amaranthus Palmeri ◽

Single Application ◽

Soybean Yield ◽

Herbicide Treatments

Palmer amaranth (Amaranthus palmeri S. Wats.) is one of the most difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. Research was conducted during 2010 and 2011 to determine if Palmer amaranth control and soybean yield were affected by soybean plant population and combinations of preemergence (PRE) herbicides followed by a single application of glufosinate postemergence (POST) versus multiple applications of glufosinate POST. Palmer amaranth was controlled more and soybean yield was greater when soybean was established at 483,000 plants ha−1 in 3 of 4 experiments compared with soybean at 178,000 plants ha−1 irrespective of herbicide treatments. In separate experiments, application of PRE herbicides followed by POST application of glufosinate or multiple POST applications of glufosinate provided variable Palmer amaranth control, although combinations of PRE and POST herbicides controlled Palmer amaranth the most and provided the greatest soybean yield. In 1 of 3 experiments, sequential applications of glufosinate were more effective than a single application. Yield was higher in 2 of 3 experiments when glufosinate was applied irrespective of timing of application when compared with the nontreated control. In the experiment where glufosinate was applied at various POST timings, multiple applications of the herbicide provided the best control and the greatest yield compared with single applications.

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Weed Control for Close-Drilled Soybeans

Weed Science ◽

10.1017/s0043174500034834 ◽

1972 ◽

Vol 20 (1) ◽

pp. 16-19 ◽

Cited By ~ 3

Author(s):

L. M. Wax

Keyword(s):

Glycine Max ◽

Weed Control ◽

Yield Reduction ◽

Herbicide Application ◽

Weed Species ◽

Soybean Yield ◽

Planting Time ◽

Large Numbers ◽

Seedbed Preparation

Delayed planting or “stale seedbed” for weed control in close-drilled (20-cm rows) soybeans [Glycine max(L.) Merr. ‘Amsoy’] was evaluated for 3 years. The system combined final seedbed preparation 3 to 6 weeks before planting with herbicide application at planting time. The best control of six weed species and highest soybean yields were obtained bya,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) application at the time of seedbed preparation followed by 3-(3,4-dichlorophenyl)-1-methylurea (linuron) application at planting and by linuron application at planting without the early trifluralin application. Applications of 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat) at planting, either with or without trifluralin treatments, resulted in less weed control and lower soybean yields than comparable treatments with linuron. However, even the best treatments failed to provide the weed control necessary to prevent substantial soybean yield reduction in heavy infestations of weeds that emerge in large numbers after planting, and that resist the phytotoxic action of the herbicides.

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Broadcast or Banded Chloramben by Tillage Variables in Soybeans

Weed Science ◽

10.1017/s0043174500036249 ◽

1972 ◽

Vol 20 (5) ◽

pp. 502-506 ◽

Cited By ~ 5

Author(s):

R. S. Moomaw ◽

L. R. Robison

Keyword(s):

Glycine Max ◽

Band Width ◽

Yield Reduction ◽

Soybean Yield ◽

Weed Growth

The herbicide 3-amino-2,5-dichlorobenzoic acid (chloramben) was applied preemergence to soybeans [Glycine max(L.) Merr.] in 1969, 1970, and 1971. Herbicide band widths were 18, 36, and 53 cm, and there was a broadcast treatment. Cultivation and rotary hoeing were also imposed on the herbicide band widths as variables. A 36-cm band of chloramben was the minimum band width used which consistently maintained soybean yield when supplemented with mechanical tillage. Broadcast treated soybeans without mechanical tillage yielded as well as handweeded soybeans in 2 of 3 years. Each 4 kg/ha of weed growth reduced soybean yield 1 kg/ha. Average weed yield reduction due to cultivation was 100, 76, and 54% in 1969, 1970, and 1971, respectively, when average weed yields were 360, 1650, and 4720 kg/ha in successive years. Rotary hoeing reduced weed growth 48% and increased soybean yield 20% in 1970 but did not significantly affect weed or soybean yields in 1969 and 1971.

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Shattercane (Sorghum bicolor) Interference in Soybean (Glycine max)

Weed Science ◽

10.1017/s0043174500056976 ◽

1992 ◽

Vol 40 (1) ◽

pp. 68-73 ◽

Cited By ~ 14

Author(s):

Gary M. Fellows ◽

Fred W. Roeth

Keyword(s):

Glycine Max ◽

Plant Height ◽

Direct Relationship ◽

Yield Loss ◽

Economic Loss ◽

Hyperbolic Function ◽

Yield Reduction ◽

Soybean Plant ◽

Soybean Yield ◽

Forage Sorghum

Shattercane interference in irrigated soybean was evaluated during 1987, 1988, and 1989 at Clay Center, NE, using ‘Rox’ forage sorghum to simulate shattercane. Soybean yield reduction did not occur if shattercane was removed by 2 wk after emergence in 1987 and 6 wk after emergence in 1988 and 1989. Shattercane interference with soybean began when shattercane height exceeded soybean height. Soybean yield was reduced up to 25% before the height differential reached 30 cm, the minimum difference required for selectively applying glyphosate with a wiper applicator. Soybean nodes per stem, pods per stem, and beans per pod decreased as duration of interference increased. A direct relationship between soybean yield loss and shattercane density fit a rectangular hyperbolic function. Yield loss per shattercane plant was highest at low shattercane densities. Soybean plant height, biomass, nodes per stem, pods per stem, pods per node, and beans per pod decreased as shattercane density increased. An interference model for estimation of soybean yield and economic loss based on shattercane density was developed.

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Common Sunflower (Helianthus annuus) Interference in Soybean (Glycine max)

Weed Technology ◽

10.1017/s0890037x00040021 ◽

1996 ◽

Vol 10 (2) ◽

pp. 317-321 ◽

Cited By ~ 14

Author(s):

Patrick W. Geier ◽

Larry D. Maddux ◽

Loren J. Moshier ◽

Phillip W. Stahlman

Keyword(s):

Dry Matter ◽

Market Price ◽

Yield Reduction ◽

Soybean Yield ◽

Sunflower Plant ◽

Matter Production ◽

Competition Study ◽

Soybean Canopy ◽

Relationship Of ◽

The Relationship

An in-row competition study was conducted in 1991 and 1992 near Silver Lake, KS to determine the relationship of noncultivated common sunflower density to soybean yield, PAR at the soybean canopy, and common sunflower dry matter production. Because of environmental differences, year main effect interactions occurred, so results are presented by year. For example, 0.3 common sunflower plant/m2produced 4030 kg/ha of aboveground dry matter in 1991 and 1300 kg/ha in 1992. Soybean yield reduction ranged from 19 and 17% with 0.3 common sunflower plant/m2to 97 and 95% with 4.6 plant/m2, in 1991 and 1992, respectively. Assuming a treatment cost of $35/ha and a soybean market price of $0.21/kg, economic threshold levels were 0.1 common sunflower plant/m2in 1991, and 0.07 in 1992. Common sunflower at 0.3 plant/m2reduced PAR at the soybean canopy by 390 and 300 μE/m2/s, or 24 and 18% in 1991 and 1992, respectively. We conclude that the ability of common sunflower to intercept PAR above the soybean canopy is an important component in its interference with soybean.

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