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

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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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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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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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 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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Suppression of Glyphosate-resistant Canada Fleabane (Conyza canadensis) in Corn with Cover Crops Seeded after Wheat Harvest the Previous Year

Weed Technology ◽

10.1017/wet.2018.19 ◽

2018 ◽

Vol 32 (3) ◽

pp. 244-250 ◽

Cited By ~ 7

Author(s):

Taïga B. Cholette ◽

Nader Soltani ◽

David C. Hooker ◽

Darren E. Robinson ◽

Peter H. Sikkema

Keyword(s):

Cover Crops ◽

Weed Management ◽

Cover Crop ◽

Management Strategies ◽

Late Summer ◽

Growing Season ◽

Integrated Weed Management ◽

Crop Species ◽

Herbicide Resistant ◽

Crimson Clover

AbstractGlyphosate-resistant (GR) and multiple herbicide–resistant (groups 2 and 9) Canada fleabane have been confirmed in 30 and 23 counties in Ontario, respectively. The widespread incidence of herbicide-resistant Canada fleabane highlights the importance of developing integrated weed management strategies. One strategy is to suppress Canada fleabane using cover crops. Seventeen different cover crop monocultures or polycultures were seeded after winter wheat harvest in late summer to determine GR Canada fleabane suppression in corn grown the following growing season. All cover crop treatments seeded after wheat harvest suppressed GR Canada fleabane in corn the following year. At 4 wk after cover crop emergence (WAE), estimated cover crop ground cover ranged from 31% to 68%, a density of 124 to 638 plants m–2, and a range of biomass from 29 to 109 g m–2, depending on cover crop species. All of the cover crop treatments suppressed GR Canada fleabane in corn grown the following growing season from May to September compared to the no cover crop control. Among treatments evaluated, annual ryegrass (ARG), crimson clover (CC)/ARG, oilseed radish (OSR)/CC/ARG, and OSR/CC/cereal rye (CR) were the best treatments for the suppression of GR Canada fleabane in corn. ARG alone or in combination with CC provided the most consistent GR Canada fleabane suppression, density reduction, and biomass reduction in corn. Grain corn yields were not affected by the use of the cover crops evaluated for Canada fleabane suppression.

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Effects of cover crop presence, cover crop species selection and fungicide seed treatment on corn seedling growth

Renewable Agriculture and Food Systems ◽

10.1017/s1742170517000345 ◽

2017 ◽

Vol 34 (2) ◽

pp. 93-102 ◽

Cited By ~ 4

Author(s):

Lara A. Schenck ◽

Matthew G. Bakker ◽

Thomas B. Moorman ◽

Thomas C. Kaspar

Keyword(s):

Environmental Quality ◽

Cover Crops ◽

Cover Crop ◽

Seed Treatment ◽

Disease Development ◽

Crop Species ◽

Cereal Rye ◽

Seedling Root ◽

Corn Seedling ◽

Negative Impacts

AbstractCover crops can offer erosion protection as well as soil and environmental quality benefits. Cereal rye (Secale cerealeL.) is the most commonly used winter cover crop in corn–soybean rotations in the upper Midwest of the USA because of its superior winter hardiness and growth at cool temperatures. Cereal rye cover crops, however, can occasionally have negative impacts on the yield of a following corn crop, which discourages broader adoption and introduces substantial risk for corn farmers employing cover crops. We hypothesized that because cereal rye shares some pathogens with corn, it may be causing increased disease in corn seedlings planted soon after cereal rye termination. To test this, we performed a series of experiments in a controlled environment chamber to assess the response of corn seedlings with and without a commercial fungicide seed treatment to the presence of cereal rye or other species of cover crops that were terminated with herbicide prior to corn planting. Our results indicate that under cool and wet conditions, cereal rye reduces corn seedling growth performance and increases incidence of corn seedling root disease. Fungicide seed treatment had limited efficacy in preventing these effects, perhaps because environmental conditions were set to be very conducive for disease development. However, hairy vetch (Vicia villosaRoth) and winter canola (Brassica napusL.) cover crops had fewer negative impacts on corn seedlings compared with cereal rye. Thus, to expand the practice of cover cropping before corn, it should become a research priority to develop alternative management practices to reduce the risk of corn seedling root infection following cereal rye cover crops. Over the longer term, testing, selection and breeding efforts should identify potential cover crop species or genotypes that are able to match the winter hardiness, growth at cool temperatures and the conservation and environmental quality benefits of cereal rye, while avoiding the potential for negative impacts on corn seedlings when environmental conditions are suitable for disease development.

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Comparison of the Allelopathic Potential of Leguminous Summer Cover Crops: Cowpea, Sunn Hemp, and Velvetbean

HortScience ◽

10.21273/hortsci.42.2.289 ◽

2007 ◽

Vol 42 (2) ◽

pp. 289-293 ◽

Cited By ~ 23

Author(s):

Michael J. Adler ◽

Carlene A. Chase

Keyword(s):

Plant Height ◽

Cover Crops ◽

Cover Crop ◽

Dry Weight ◽

Bell Pepper ◽

Weed Species ◽

Crop Species ◽

Allelopathic Potential ◽

Sunn Hemp ◽

Germination And Growth

The phytotoxicity of aqueous foliar extracts and ground dried residues of sunn hemp (Crotalaria juncea L.), cowpea [Vigna unguiculata (L.) Walp. cv. Iron Clay], and velvetbean [Mucuna deeringiana (Bort) Merr.] to crop and weed germination and growth was evaluated to compare the allelopathic potential of the cover crops. By 14 days after treatment (DAT), goosegrass [Eleusine indica (L.) Gaertn.] germination with 5% aqueous extracts of all cover crops (w/v fresh weight basis) was similar and greater than 75% of control. However, with the 10% extracts, goosegrass germination was lowest with cowpea extract, intermediate with velvetbean extract, and highest with sunn hemp extract. Livid amaranth (Amaranthus lividus L.) germination declined to ≈50% with cowpea and sunn hemp extracts and even lower to 22% with velvetbean extract. The suppression of livid amaranth germination was greater with the 10% extracts than the 5% extracts. Bell pepper (Capsicum annuum L.) germination was unaffected by velvetbean extract, inhibited more by the 5% cowpea extract than the 10% extract, and was also sensitive to the 10% sunn hemp extract. All cover crop extracts resulted in an initial delay in tomato (Lycopersicon esculentum Mill.) germination, but by 14 DAT, inhibition of germination was apparent only with cowpea extract. The phytotoxicity of ground dried residues of the three cover crops on germination, plant height, and dry weight of goosegrass, smooth amaranth (A. hybridus L.), bell pepper, and tomato was evaluated in greenhouse studies. Goosegrass germination was inhibited in a similar manner by residues of the three cover crops to 80% or less of control. Smooth amaranth germination, plant height, and dry biomass were more sensitive to sunn hemp residues than to cowpea and velvetbean residues. Bell pepper germination, plant height, and dry weight were greater than 90% of control except for dry weight with cowpea residue, which was only 78% of control. The greatest effect of cover crop residue on tomato occurred with dry weight, because dry weights with cowpea and sunn hemp were only 76% and 69% of control, respectively, and lower than with velvetbean. There was more evidence of cover crop phytotoxicity with the weed species than with the crop species and cowpea extracts and residue affected all species more consistently than those of sunn hemp and velvetbean.

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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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Weed Suppression in Cover Crop Monocultures and Mixtures

Weed Science ◽

10.1017/wsc.2017.59 ◽

2017 ◽

Vol 66 (1) ◽

pp. 121-133 ◽

Cited By ~ 36

Author(s):

Barbara Baraibar ◽

Mitchell C. Hunter ◽

Meagan E. Schipanski ◽

Abbe Hamilton ◽

David A. Mortensen

Keyword(s):

Ecosystem Services ◽

Cover Crops ◽

Cover Crop ◽

Biomass Accumulation ◽

Weed Suppression ◽

Species Selection ◽

Grass Species ◽

Weed Seed ◽

Crop Species ◽

Cereal Rye

Interest in planting mixtures of cover crop species has grown in recent years as farmers seek to increase the breadth of ecosystem services cover crops provide. As part of a multidisciplinary project, we quantified the degree to which monocultures and mixtures of cover crops suppress weeds during the fall-to-spring cover crop growing period. Weed-suppressive cover crop stands can limit weed seed rain from summer- and winter-annual species, reducing weed population growth and ultimately weed pressure in future cash crop stands. We established monocultures and mixtures of two legumes (medium red clover and Austrian winter pea), two grasses (cereal rye and oats), and two brassicas (forage radish and canola) in a long fall growing window following winter wheat harvest and in a shorter window following silage corn harvest. In fall of the long window, grass cover crops and mixtures were the most weed suppressive, whereas legume cover crops were the least weed suppressive. All mixtures also effectively suppressed weeds. This was likely primarily due to the presence of fast-growing grass species, which were effective even when they were seeded at only 20% of their monoculture rate. In spring, weed biomass was low in all treatments due to winter kill of summer-annual weeds and low germination of winter annuals. In the short window following silage corn, biomass accumulation by cover crops and weeds in the fall was more than an order of magnitude lower than in the longer window. However, there was substantial weed seed production in the spring in all treatments not containing cereal rye (monoculture or mixture). Our results suggest that cover crop mixtures require only low seeding rates of aggressive grass species to provide weed suppression. This creates an opportunity for other species to deliver additional ecosystem services, though careful species selection may be required to maintain mixture diversity and avoid dominance of winter-hardy cover crop grasses in the spring.

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Cultivation and Interseeding for Weed Control in Transplanted Cabbage

Weed Technology ◽

10.1614/wt-03-157r ◽

2004 ◽

Vol 18 (3) ◽

pp. 704-710 ◽

Cited By ~ 11

Author(s):

Daniel C. Brainard ◽

Robin R. Bellinder ◽

Andrew J. Miller

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Field Trials ◽

Integrated System ◽

Weed Suppression ◽

Yield Losses ◽

Hairy Vetch ◽

Crop Species ◽

Yield Penalty ◽

Additional Nitrogen

Multiple means of overcoming interspecific competition between transplanted cabbage and interseeded cover crops were studied in field trials conducted from 1995 to 2001. Cover crop species and time of seeding (1995 and 1996), use of supplemental nitrogen (1997 and 1998), and herbicide regulation (1999 and 2001) were evaluated with the objective of integrating soil-improving cover crops into cabbage production while facilitating weed suppression with minimal use of herbicides. Cabbage was cultivated at 10, 10 + 20, or 10 + 20 + 30 d after transplanting (DAT) with or without cover crops (hairy vetch, lana vetch, or oats) sown at the time of the last cultivation. Early interseeding (10 DAT) of all species significantly reduced cabbage yields. Both vetches could be sown 20 or 30 DAT without a yield penalty. However, weed suppression was not consistently greater than cultivation without cover crops. Spring oats were unacceptably competitive, even when sown 30 DAT in some years. With additional nitrogen, cabbage yields were consistently increased, but the increases were not directly related to decreased competition from either weeds or cover crops. The potential for herbicide regulation of cover crops to prevent cabbage yield losses could not be evaluated because cabbage yields were not reduced by cover crops in 1999 and 2001. Although interseeded crops did not generally provide significant in-season weed suppression compared with cultivation alone, the lack of yield penalty and the potential soil-improving qualities of legumes may justify interseeding hairy vetch at 20 DAT in an integrated system.

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