Mechanisms of Weed Suppression in Cover Crop-based Production Systems

Field and laboratory studies were conducted to investigate the mechanisms of weed suppression by cover crops. High-performance liquid chromatograph analysis and a seed germination bioassay demonstrated that rye (Secale cereale L.) can be leached of its allelochemicals, redried, and used as an inert control for separating physical suppression from other types of interference. In a field study, rye, crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth.), barley (Hordeum vulgare L.), and a mixture of the four species suppressed the emergence of eastern black nightshade (Solanum ptycanthum Dun.). Crimson clover inhibited the emergence of eastern black nightshade beyond what could be attributed to physical suppression alone. The emergence of yellow foxtail [Setaria glauca (L.) Beauv.] was inhibited by rye and barley but not by the other cover crops or the cover crop mixture.

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Comparison of Mixtures vs. Monocultures of Cover Crops for Fresh-market Tomato Production With and Without Herbicide

HortScience ◽

10.21273/hortsci.33.7.1163 ◽

1998 ◽

Vol 33 (7) ◽

pp. 1163-1166 ◽

Cited By ~ 43

Author(s):

John R. Teasdale ◽

Aref A. Abdul-Baki

Keyword(s):

Cover Crops ◽

Cover Crop ◽

C:N Ratio ◽

Weed Suppression ◽

Hairy Vetch ◽

Fresh Market ◽

Vicia Villosa ◽

Tomato Production ◽

Crimson Clover ◽

Marketable Fruit

Hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) and mixtures of rye with hairy vetch and/or crimson clover were compared for no-tillage production of staked, fresh-market tomatoes (Lycopersicon esculentum Mill.) on raised beds. All cover crops were evaluated both with or without a postemergence application of metribuzin for weed control. Biomass of cover crop mixtures were higher than that of the hairy vetch monocrop. Cover crop nitrogen content varied little among legume monocrops and all mixtures but was lower in the rye monocrop. The C:N ratio of legume monocrops and all mixtures was <30 but that of the rye monocrop was >50, suggesting that nitrogen immobilization probably occurred only in the rye monocrop. Marketable fruit yield was similar in the legume monocrops and all mixtures but was lower in the rye monocrop when weeds were controlled by metribuzin. When no herbicide was applied, cover crop mixtures reduced weed emergence and biomass compared to the legume monocrops. Despite weed suppression by cover crop mixtures, tomatoes grown in the mixtures without herbicide yielded lower than the corresponding treatments with herbicide in 2 of 3 years. Chemical name used: [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one](metribuzin).

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Allelopathy in Cover Crop-based Production Systems

HortScience ◽

10.21273/hortsci.30.4.819a ◽

1995 ◽

Vol 30 (4) ◽

pp. 819A-819

Author(s):

N.G. Creamer ◽

M.A. Bennett ◽

J. Cardina ◽

E.E. Regnier

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Production Systems ◽

Single Species ◽

Crop Species ◽

Eastern Black Nightshade ◽

Crimson Clover ◽

Water Ph ◽

Germinating Seeds ◽

Allelochemical Effects

Little research has been conducted to quantify allelopathic suppression of weeds in the field. The objectives of this study were to develop an adequate control for separating physical from allelochemical effects, use the control to quantify allelochemical suppression in the field, and determine whether a mixture of cover crops would provide a broader spectrum of weed control than single species. Hairy vetch, rye, crimson clover, and barley were cut into 5-cm pieces, shaken in distilled water (pH 6) to leach allelochemicals, and redried. A seed germination bioassay confirmed that leached cover crops were nontoxic to germinating seeds. Physical suppression of Eastern black nightshade by the four cover crop species occurred in the field study, as did allelochemical suppression by crimson clover. Only rye physically suppressed yellow foxtail, and none of the cover crops suppressed yellow foxtail allelochemically.

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Carryover of Common Corn and Soybean Herbicides to Various Cover Crop Species

Weed Technology ◽

10.1614/wt-d-16-00062.1 ◽

2017 ◽

Vol 31 (1) ◽

pp. 21-31 ◽

Cited By ~ 19

Author(s):

Cody D. Cornelius ◽

Kevin W. Bradley

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Production Systems ◽

Italian Ryegrass ◽

Hairy Vetch ◽

Crop Species ◽

Cereal Rye ◽

Crimson Clover ◽

Crop Establishment ◽

Biomass Reduction

The recent interest in cover crops as component of Midwest corn and soybean production systems has led to the need for additional research, including the effects of residual corn and soybean herbicide treatments on fall cover crop establishment. Field studies were conducted in 2013, 2014, and 2015 in Columbia, Missouri to investigate the effects of common residual herbicides applied in corn and soybean on establishment of winter wheat, tillage radish, cereal rye, crimson clover, winter oat, Austrian winter pea, Italian ryegrass, and hairy vetch. Cover crops were evaluated for stand and biomass reduction 28 d after emergence (DAE). Rainfall from herbicide application to cover crop seeding date was much greater in 2014 and 2015, which resulted in less carryover in these years compared to 2013. When averaged across all herbicides evaluated in these experiments, the general order of sensitivity of cover crops to herbicide carryover, from greatest to least was Austrian winter pea=crimson clover>oilseed radish>Italian ryegrass>hairy vetch>wheat >winter oat>cereal rye. Cereal rye had the fewest instances of biomass or stand reduction with only four out of the 27 herbicides adversely effecting establishment. Pyroxasulfone consistently reduced Italian ryegrass and winter oat biomass at least 67% in both the corn and soybean experiments. In the soybean experiment, imazethapyr- and fomesafen-containing products resulted in severe stand and biomass reduction in both years while flumetsulam-containing products resulted in the greatest carryover symptoms in the corn experiment. Results from these experiments suggest that several commonly used corn and soybean herbicides have the potential to hinder cover crop establishment, but the severity of damage will depend on weather, cover crop species, and the specific herbicide combination.

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Herbicide selection to terminate grass, legume, and brassica cover crop species

Weed Technology ◽

10.1017/wet.2019.107 ◽

2019 ◽

Vol 34 (1) ◽

pp. 48-54

Author(s):

Kara B. Pittman ◽

Charles W. Cahoon ◽

Kevin W. Bamber ◽

Lucas S. Rector ◽

Michael L. Flessner

Keyword(s):

Active Ingredient ◽

Cover Crops ◽

Cover Crop ◽

Field Studies ◽

Weed Suppression ◽

Hairy Vetch ◽

Crop Species ◽

Rating Data ◽

Crimson Clover ◽

And Control

AbstractCover crops provide a number of agronomic benefits, including weed suppression, which is important as cases of herbicide resistance continue to rise. To effectively suppress weeds, high cover crop biomass is needed, which necessitates later termination timing. Cover crop termination is important to mitigate potential planting issues and prevent surviving cover crop competition with cash crops. Field studies were conducted in Virginia to determine the most effective herbicide options alone or combined with glyphosate or paraquat to terminate a range of cover crop species. Results revealed that grass cover crop species were controlled (94% to 98%) by glyphosate alone 4 wk after application (WAA). Overall, legume species varied in response to the single active-ingredient treatments, and control increased with the addition of glyphosate or paraquat. Mixes with glyphosate provided better control of crimson clover and hairy vetch by 7% to 8% compared with mixes containing paraquat 4 WAA. Mix partner did not influence control of Austrian winter pea. No treatment adequately controlled rapeseed in this study, with a maximum of 58% control observed with single active-ingredient treatments and 62% control with mixes. Height reduction for all cover crop species supports visible rating data. Rapeseed should be terminated when smaller, which could negate weed suppressive benefits from this cover crop species. Growers should consider herbicide selection and termination timing in their cover crop plan to ensure effective termination.

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Herbicide Programs for the Termination of Various Cover Crop Species

Weed Technology ◽

10.1017/wet.2017.20 ◽

2017 ◽

Vol 31 (4) ◽

pp. 514-522 ◽

Cited By ~ 5

Author(s):

Cody D. Cornelius ◽

Kevin W. Bradley

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Field Experiments ◽

Crop Yields ◽

Production Systems ◽

Annual Ryegrass ◽

Crop Species ◽

Cereal Rye ◽

Crimson Clover ◽

Herbicide Treatments

The recent interest in cover crops as a component of Midwest corn and soybean production systems has led to a greater need to understand the most effective herbicide treatments for cover crop termination prior to planting corn or soybean. Previous research has shown that certain cover crop species can significantly reduce subsequent cash crop yields if not completely terminated. Two field experiments were conducted in 2013, 2014, and 2015 to determine the most effective herbicide program for the termination of winter wheat, cereal rye, crimson clover, Austrian winter pea, annual ryegrass, and hairy vetch; and cover crops were terminated in early April or early May. Visual control and above ground biomass reduction was determined 28 d after application (DAA). Control of grass cover crop species was often best with glyphosate alone or combined with 2,4-D, dicamba, or saflufenacil. The most consistent control of broadleaf cover crops occurred following treatment with glyphosate +2,4-D, dicamba, or saflufenacil. In general, control of cover crops was higher with early April applications compared to early May. In a separate study, control of 15-, 25-, and 75-cm tall annual ryegrass was highest with glyphosate at 2.8 kg ha−1or glyphosate at 1.4 kg ha−1plus clethodim at 0.136 kgha−1. Paraquat- or glufosinate-containing treatments did not provide adequate annual ryegrass control. For practitioners who desire higher levels of cover crop biomass, these results indicate that adequate levels of cover crop control can still be achieved in the late spring with certain herbicide treatments. But it is important to consider cover crop termination well in advance to ensure the most effective herbicide or herbicide combinations are used and the products are applied at the appropriate stage.

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COVER CROP AND NITROGEN FERTILIZER RATE INFLUENCES ON YIELDS OF SEQUENTIALLY PLANTED VEGETABLES

HortScience ◽

10.21273/hortsci.27.6.570c ◽

1992 ◽

Vol 27 (6) ◽

pp. 570c-570

Author(s):

Owusu A. Bandele ◽

Marion Javius ◽

Byron Belvitt ◽

Oscar Udoh

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Fertilizer Rate ◽

Vicia Villosa ◽

Trifolium Incarnatum ◽

Crimson Clover ◽

Summer Squash ◽

Nitrogen Fertilizer Rate ◽

Mustard Green ◽

N Rates

Fall-planted cover crops of hairy vetch (Vicia villosa Roth), Austrian winter pea (Pisum sativum subsp. arvense L. Poir), and crimson clover (Trifolium incarnatum L.) were each followed by spring-planted 'Sundance' summer squash [Cucurbita pepo var. melopepo (L.) Alef.] and 'Dasher' cucumber (Cucumis sativus L.). Squash and cucumber crops were followed by fall 'Florida Broadleaf mustard green [Brassica juncea (L.) Czerniak] and 'Vates' collard (Brassica oleracea L. Acephala group), respectively. The same vegetable sequences were also planted without benefit of cover crop. Three nitrogen (N) rates were applied to each vegetable crop. Squash following winter pea and crimson clover produced greater yields than did squash planted without preceding cover crop. Cucumber following crimson clover produced the greatest yields. No cover crop effect was noted with mustard or collard. Elimination of N fertilizer resulted in reduced yields for all crops, but yields of crops with one-half the recommended N applied were generally comparable to those receiving the full recommended rate.

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Effects of Long-Term Cover Cropping on Weed Seedbanks

Frontiers in Agronomy ◽

10.3389/fagro.2020.591091 ◽

2020 ◽

Vol 2 ◽

Author(s):

Virginia Nichols ◽

Lydia English ◽

Sarah Carlson ◽

Stefan Gailans ◽

Matt Liebman

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Production Systems ◽

Early Spring ◽

Weed Suppression ◽

Winter Rye ◽

Maize Crop ◽

Cover Cropping ◽

Crop Biomass

Cool-season cover crops have been shown to reduce soil erosion and nutrient discharge from maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] production systems. However, their effects on long-term weed dynamics are not well-understood. We utilized five long-term research trials in Iowa to quantify germinable weed seedbank densities and compositions after 10+ years of cover cropping treatments. All five trials consisted of zero-tillage maize-soybean rotations managed with and without the inclusion of a yearly winter rye (Secale cereal L.) cover crop. Seedbank sampling was conducted in the early spring before crop planting at all locations, with three of the five trials having grown a soybean crop the preceding year, and two a maize crop. Two of the trials (both previously soybean) showed significant and biologically relevant decreases (4,070 and 927 seeds m−2, respectively) in seedbank densities in cover crop treatments compared to controls. In another two trials, one previously maize and one previously soybean, no difference was detected in seedbank densities. In the fifth trial (previously maize), there was a significant, but biologically unimportant increase of 349 seeds m−2. All five trials' weed communities were dominated by common waterhemp [Amaranthus tuberculatus (Moq.)], and changes in seedbank composition from cover-cropping were driven by changes in this species. Although previous studies have shown that increases in cover crop biomass are strongly correlated with weed suppression, in our study we did not find a relationship between seedbank changes and the mean amount of cover crop biomass produced over a 10-years period (experiment means ranging from 0.5 to 2.0 Mg ha−1 yr−1), the stability of the cover crop biomass production, nor the amount produced going into the previous crop's growing season. We conclude that long-term use of a winter rye cover crop in a maize-soybean system has the potential to meaningfully reduce the size of weed seedbanks compared to winter fallows. However, identifying the mechanisms by which this occurs requires further research into processes such as seed predation and seed decay in cover cropped systems.

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Allelopathic Impact of Cover Crop Species on Soybean and Goosegrass Seedling Germination and Early Growth

Agriculture ◽

10.3390/agriculture11100965 ◽

2021 ◽

Vol 11 (10) ◽

pp. 965

Author(s):

Kendall Sheldon ◽

Sam Purdom ◽

Avat Shekoofa ◽

Larry Steckel ◽

Virginia Sykes

Keyword(s):

Cover Crops ◽

Root Length ◽

Cover Crop ◽

Deionized Water ◽

Weed Suppression ◽

Crop Species ◽

Allelopathic Potential ◽

Row Crops ◽

Crimson Clover ◽

Seedling Root

Cover crops can provide a variety of benefits to an agricultural system: weed suppression, soil quality improvement, and soil water infiltration. Although there is ample research documenting weed suppression from cover crops, the mechanics of the suppression are not implicitly understood. Along with the aforementioned positive attributes, negative allelopathic effects on row crops planted into cover crop systems have been documented. The objective of this study was to evaluate the allelopathic potential of certain cover crop species on soybean (Glycine max L.) and goosegrass (Eleusine indica L.) germination and early seedling growth under controlled environments in petri dish and pot experiments. Leachates from above-ground biomass of five cover crop species, wheat (Triticum aestivum L.), cereal rye (Secale cereale), hairy vetch (Vicia villosa), crimson clover (Trifolium incarnatum L.), and canola (Brassica napus L.), from two locations (East and Middle Tennessee) were extracted and applied at 0 (water) and 50 v/v. In experiment I, both soybean and goosegrass seeds were examined, and, in experiment II, only soybean seeds were examined under the application of cover crop leachates. Most cover crop leachates from both locations significantly reduced the soybean seedling root length (p < 0.01). Overall, the application of canola extract (East Tennessee) suppressed soybean seed germination the most (28%) compared to deionized water. For goosegrass, the wheat cover crop leachate significantly reduced seedling root length (p < 0.01). In experiment II, the soybean root nodulation was significantly increased with the wheat extract treatment compared to deionized water. While the results indicate that the location and environment may change cover crop species allelopathic potential, the wheat cover crop leachate had the most potent allelopathic impact on goosegrass germination and growth; however, had the lowest observed adverse effect on our tested row crop, soybean.

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A method for mechanically killing cover crops to optimize weed suppression

American Journal of Alternative Agriculture ◽

10.1017/s0889189300006408 ◽

1995 ◽

Vol 10 (4) ◽

pp. 157-162 ◽

Cited By ~ 27

Author(s):

N.G. Creamer ◽

B. Plassman ◽

M.A. Bennett ◽

R.K. Wood ◽

B.R. Stinner ◽

...

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Crop Residues ◽

Subterranean Clover ◽

Soil Surface ◽

Weed Suppression ◽

Hairy Vetch ◽

Mechanical Method ◽

Crop Species ◽

Crimson Clover

AbstractResidues of dead cover crops can suppress weeds by providing a mulch on the soil surface. The cover crop usually is killed with herbicides, but a mechanical method is desirable in systems intended to reduce chemical use. We designed and built an undercutter to kill cover crops by severing their roots while flattening the intact aboveground biomass on the surface of raised beds. We studied which cover crop species could be killed with the undercutter and compared the weed control potential of cover crop residues after flail mowing, sicklebar mowing, and undercutting.Whether a species was killed by the undercutter depended primarily on growth stage. Species that were in mid- to late bloom or beyond, including rye, hairy vetch, bigflower vetch, crimson clover, barley, and subterranean clover, were easily killed by undercutting. There were no differences in dry weights of broadleaf weeds between the undercut and simulated sicklebar mowed treatments, both of which had less weed biomass than the clean-tilled or flail-mowed plots.

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Evaluating cereal rye and crimson clover for weed suppression within buffer areas in dicamba-resistant soybean

Weed Technology ◽

10.1017/wet.2020.121 ◽

2020 ◽

pp. 1-29

Author(s):

Connor L. Hodgskiss ◽

Bryan G. Young ◽

Shalamar D. Armstrong ◽

William G. Johnson

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Early Summer ◽

Weed Suppression ◽

Weed Species ◽

Cereal Rye ◽

Herbicide Resistant ◽

Crimson Clover ◽

Emergence Patterns ◽

Crop Biomass

Abstract As herbicide-resistant weeds become more problematic, producers will consider the use of cover crops to suppress weeds. Weed suppression from cover crops may be especially in the label-mandated buffer areas of dicamba-resistant soybean where dicamba use is not allowed. Three cover crops terminated at three timings with three herbicide strategies were evaluated for their effect on weed suppression in dicamba-resistant soybean. Delaying termination to at soybean planting, or after, and using a cereal rye or cereal rye + crimson clover increased cover crop biomass by at least 40% compared to terminating early or using a crimson clover only cover crop. Densities of problematic weed species were evaluated in early-summer prior to a blanket POST application. Plots with cereal rye had 75% less horseweed compared to crimson clover at two of four site-years. Cereal rye or the mix cover crop terminated at, or after soybean planting reduced waterhemp densities by 87% compared to early termination timings of crimson clover and the earliest termination timing of the mix at one of two site-years. Cover crops were not as effective in reducing waterhemp densities as they were in reducing horseweed densities. This difference is due to a divergence in emergence patterns; waterhemp emergence generally peaks after termination of the cover crop while horseweed emergence coincides with establishment and rapid vegetative growth of cereal rye. Cover crops alone were generally not as effective as using a high biomass cover crop combined with herbicide strategy that contained dicamba and residual herbicides. However, within label-mandated buffer areas where dicamba cannot be used, a cover crop containing cereal rye with delayed termination to at soybean planting combined with residual herbicides could be utilized to improve suppression of horseweed and waterhemp.

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