Predictive phytotoxic value of water-soluble allelochemicals in plant extracts for choosing a cover crop or mulch for specific weed control

Cover crops and mulches have become an alternative for soil management in vineyards due to the agronomic, environmental, and economic advantages, especially the possibility of weed control. Implicitly to this objective lies the idea of assessing the potential herbicide effect of the allelochemicals released by different cover crop and mulch species. With this objective, the present work evaluated the phytotoxic effects of 12 aqueous extracts of selected species with potential use as a cover crop or mulch: a Bromus species mixture (B. hordeaceus L. and B. rubens L.), Festuca arundinacea Schreb., Hordeum murinum L., H. vulgare L., Vulpia ciliata Dumort., Medicago rugosa Desr., M. sativa L., Trifolium subterraneum L., T. incarnatum L., Phacelia tanacetifolia Benth., Sinapis alba L., and Pinus sylvestris L.,on the germination and early growth of three troublesome weeds (Conyza bonariensis (L.) Cronquist, Aster squamatus (Spreng.) Hieron, and Bassia scoparia (L.) A. J.). The different in vitro bioassays showed that aqueous extracts of some species significantly inhibited or reduced germination and root and shoot growth of the target weed species in a dose-response manner. Germination of A. squamatus and C. bonariensis was reduced by 100-80% by the different extracts applied at 50% concentration, and completely blocked at 100% concentration, except for M rugosa extract to which both species showed less sensitivity. Root elongation of A. squamatus was absolutely inhibited under every extract and concentration, whereas C. bonariensis root growth showed only some tolerance to the crude extracts of F. arundinaceaand P. sylvestris. Bassia scoparia was relatively tolerant to the aqueous plant extracts, except for T. subterraneum crude extract, which reduced total germination by 80%; otherwise, B. scoparia showed higher general sensitivity of shoot growth than the other two weed species. The chemical profiles of phenolic compounds of the aqueous extracts were obtained and identified by HPLC-DAD, the phenolic profiles of H. murinum, V. ciliata, and M. rugosa being reported in this work for the first time. Using stepwise regression, the influence of certain phenolic compounds from the aqueous extracts on the germination and early growth of weeds was predicted. Among other significant compounds, the flavonoid naringenin identified in T. subterraneumaqueous extract at 8.09 µg·mL-1 was predicted to underlie its specific phytotoxicity on B. scoparia germination. These results support the use of cover crops and mulches in weed management and can help to select the most suitable species to adopt according to the target weed species. Highlights The phytotoxic nature of the aqueous extracts of twelve conventional and novel cover crops and mulch species was demonstrated on three troublesome weed species in vineyards. Phenolic acids and flavonoids of the twelve aqueous extracts were identified and quantified by HPLC-DAD, and, by regression analysis, some allelochemicals were postulated as responsible for the phytotoxic effects. The water-soluble phenolic profiles of three potential cover crops, namely Hordeum murinum, Vulpia ciliata, and Medicago rugosa, are reported for the first time. In vitro germination and early root growth of Conyza bonariensis and Aster squamatus were almost entirely restricted by any of the twelve plants' aqueous extracts and presumably by the joint action of their particular allelopathic compounds. Bassia scoparia germination was relatively much less sensitive to the extracts, except for Trifolium subterraneum, for which the flavonoid naringenin was predicted to underlie its specific phytotoxicity.

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Rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.) cover crops can increase their allelopathic potential for weed control when used mixed as dead mulch

Italian Journal of Agronomy ◽

10.4081/ija.2021.1869 ◽

2021 ◽

Cited By ~ 1

Author(s):

Lara Abou Chehade ◽

Carolina G. Puig ◽

Carlos Souto ◽

Daniele Antichi ◽

Marco Mazzoncini ◽

...

Keyword(s):

Cover Crops ◽

Secale Cereale ◽

Cover Crop ◽

Crop Residues ◽

Aqueous Extracts ◽

Inhibitory Effects ◽

Weed Species ◽

Allelopathic Potential ◽

Better Than

Cover crops are essential tools in agroecosystems for reducing the reliance on synthetic inputs and associated environmental risks. Alongside their benefits to soil fertility, cover crops can control weeds by their competitive and allelopathic attributes. Laboratory and field experiments were conducted to assess the allelopathic potential of two cover crop species, rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.), alone or in mixture, on seed germination and growth of arable weeds. Aqueous extracts of the two cover crops and their mixture were tested in a bioassay on Conyza canadensis (L). Cronq., Amaranthus retroflexus L. and Digitaria sanguinalis (L.) Scop. In vitro effects of aqueous extracts varied in a dose-dependent manner, with cover crops and weed species. All three extracts were able to reduce the germination of A. retroflexus (-87%) considerably. Inhibitory effects by rye and mixture extracts on radicle growth of all weed species ranged between 51 and 82%. Rye extract was the best at reducing shoot length of C. canadensis and D. sanguinalis (-39 to 44%), while squarrose clover was more effective on A. retroflexus (-79%). Plant extracts also delayed the germination time of weed species with substantial effect of the mixture on C. canadensisseeds. In the field experiment, no significant weed suppression was provided by cover crop residues incorporated as green manure compared to control plots, despite tillage being more effective in reducing weed density. Still, the cover crop mixture mulch controlled weed emergence significantly better than single cover crop mulches. The chemical characterization of cover crop residues, both shoots and roots, revealed a notable richness of allelopathic phenolic acids and flavonoids, that through slow decomposition may constitute potential natural herbicides. From the analysis of the aqueous extracts, other non-analyzed and/or unidentified water-soluble allelopathic compounds should underlie the phytotoxicity observed in vitro, at least for rye. For cover crop mixture, positive interactions among plant materials leading to a better release of allelochemicals and weeding effectiveness are discussed according to chemical profiles and field data. Our study demonstrated the allelopathic activity of the cover crops and their potential to be included in weed management strategies according to cropping system needs. Additional trials are needed to confirm the performance of cover crop residues under field conditions. Highlights - Rye and squarrose clover are cover crops with potential allelopathic effects. - Aqueous extracts of residues of rye, squarrose clover and their mixture reduced and/or slowed weed germination of A. retroflexus and C. canadensis in in vitro bioassays. - The aqueous extracts, depending on the concentration of residues, had inhibitory effects on radicle and shoot growth of A. retroflexus, C. canadensis and D. sanguinalis. - Under field conditions, mulch of a mix of rye and squarrose clover suppressed weeds better than the single species.

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Effects of Some Cover Crops on Light Extinction and Weed Coverage in Sunflower Field

Cercetari Agronomice in Moldova ◽

10.2478/cerce-2014-0014 ◽

2014 ◽

Vol 47 (2) ◽

pp. 29-40 ◽

Cited By ~ 1

Author(s):

S. Hassannejad ◽

A.R. Mobli

Keyword(s):

Extinction Coefficient ◽

Cover Crops ◽

Cover Crop ◽

Agricultural Research ◽

Block Design ◽

Light Extinction ◽

Research Station ◽

Hairy Vetch ◽

Weed Species ◽

Weed Cover

Abstract In order to evaluate the effects of some cover crops on extinction coefficient and weed cover percentage in sunflower, a field experiment was conducted based on a randomized complete block design with nine treatments and three replicates at the Agricultural Research Station, Tabriz University of Iran, during growing season 2012-2013. Treatments were triticale, hairy vetch, rapeseed, triticale + hairy vetch, triticale + rapeseed, hairy vetch + rapeseed, application of trifluralin herbicide, and controls (weed infested and weed free without planting cover crop). Result indicated than once established, living mulches can rapidly occupy the open space between the rows of the main crop and use the light that would otherwise be available to weeds. In the all cover crops treatments, the light extinction coefficient was increased and weed cover percentage was reduced. Highest reduction in total weed species was observed in hairy vetch + rapeseed and triticale + rapeseed cover crop 61.92% and 61.43 %, respectively, compared to weed infested, so this treatment was better than trifluralin application. It concluded that cover crops could be considered as integrated strategies for weed sustainable management.

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Allelopathic Influence of Germinating Seeds and Seedlings of Cover Crops on Weed Species

Weed Science ◽

10.1017/s0043174500094376 ◽

1996 ◽

Vol 44 (3) ◽

pp. 579-584 ◽

Cited By ~ 46

Author(s):

Melinda L. Hoffman ◽

Leslie A. Weston ◽

John C. Snyder ◽

Emilie E. Regnier

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Resource Competition ◽

Petri Dish ◽

Dry Weight ◽

Weed Species ◽

Allelopathic Potential ◽

Below Ground ◽

Allelopathic Interference ◽

Radicle Length

Bioassays using binary mixtures that included a cover crop with known allelopathic potential and a weed species were employed to determine the importance of allelopathy compared to resource competition as interference mechanisms. Responses of weed species germinated with cover crops in a petri dish were measured. Interference between weed and cover crop seedlings was determined in a greenhouse experiment using the additive design, which included partitions to reduce above- and below-ground competition and used capillary mat subirrigation to control moisture and fertilizer availability. Germinating sorghum reduced radicle length of weeds, whereas germinating rye tended to increase weed radicle length. Methods limited above-ground competition, so likely interference mechanisms were below-ground competition and allelopathy. Germination with a cover crop had little effect on germination and shoot length of weeds. Increased density of rye but not of sorghum reduced growth of barnyardgrass seedlings. Reduced number of barnyardgrass leaves in the presence of rye was likely due to allelopathy. Suppression of barnyardgrass dry weight attributed to allelopathic interference by rye was successfully separated and compared to the combined effects of competition and allelopathy.

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Factors Associated with Leguminous Green Manure Incorporation and Fusarium Wilt Suppression in Watermelon

Plant Disease ◽

10.1094/pdis-08-15-0956-re ◽

2016 ◽

Vol 100 (9) ◽

pp. 1910-1920 ◽

Cited By ~ 3

Author(s):

J. Himmelstein ◽

J. E. Maul ◽

Y. Balci ◽

K. L. Everts

Keyword(s):

Soil Respiration ◽

Fusarium Wilt ◽

Cover Crops ◽

Trichoderma Harzianum ◽

Cover Crop ◽

Green Manure ◽

Arbuscular Mycorrhizae ◽

Green Manures ◽

Trifolium Incarnatum

Fall-planted Vicia villosa or Trifolium incarnatum cover crops, incorporated in spring as a green manure, can suppress Fusarium wilt (Fusarium oxysporum f. sp. niveum) of watermelon. During cover crop growth, termination, and incorporation into the soil, many factors such as arbuscular mycorrhizae colonization, leachate, and soil respiration differ. How these cover-crop-associated factors affect Fusarium wilt suppression is not fully understood. Experiments were conducted to evaluate how leachate, soil respiration, and other green-manure-associated changes affected Fusarium wilt suppression, and to evaluate the efficacy of the biocontrol product Actinovate AG (Streptomyces lydicus WYEC 108). General and specific suppression was examined in the field by assessing the effects of cover crop green manures (V. villosa, T. incarnatum, Secale cereale, and Brassica juncea) on soil respiration, presence of F. oxysporum spp., and arbuscular mycorrhizal colonization of watermelon. Cover crop treatments V. villosa, T. incarnatum, and S. cereale and no cover crop were evaluated both alone and in combination with Actinovate AG in the greenhouse. Additionally, in vitro experiments were conducted to measure the effects of cover crop leachate on the mycelial growth rates of F. oxysporum f. sp. niveum race 1 and Trichoderma harzianum. Soil microbial respiration was significantly elevated in V. villosa and Trifolium incarnatum treatments both preceding and following green manure incorporation, and was significantly negatively correlated with Fusarium wilt, suggesting that microbial activity was higher under the legumes, indicative of general suppression. Parallel to this, in vitro growth rates of F. oxysporum f. sp. niveum and Trichoderma harzianum on V. villosa leachate amended media were 66 and 213% greater, respectively, than on nonamended plates. The F. oxysporum spp. population (based on CFU and not differentiated into formae specialis or races) significantly increased in V. villosa-amended field plots. Additionally, the percentage of watermelon roots colonized by arbuscular mycorrhizae following V. villosa and Trifolium incarnatum green manures was significantly higher than in watermelon following bare ground (58 and 44% higher, respectively). In greenhouse trials where cover crops were amended to soil, Actinovate AG did not consistently reduce Fusarium wilt. Both general and specific disease suppression play a role in reducing Fusarium wilt on watermelon.

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Invertebrate Seed Predators Reduce Weed Emergence Following Seed Rain

Weed Science ◽

10.1614/ws-d-15-00111.1 ◽

2016 ◽

Vol 64 (1) ◽

pp. 80-86 ◽

Cited By ~ 11

Author(s):

Carmen K. Blubaugh ◽

Ian Kaplan

Keyword(s):

Seed Predation ◽

Cover Crops ◽

Cover Crop ◽

Propagule Pressure ◽

Seedling Emergence ◽

Seed Rain ◽

Weed Species ◽

Seed Predator ◽

Common Lambsquarters ◽

Seed Predators

Weeds are selected to produce overwhelming propagule pressure, and while vertebrate and invertebrate seed predators destroy a large percentage of seeds, their ecosystem services may not be sufficient to overcome germination site limitations. Cover crops are suggested to facilitate seed predation, but it is difficult to disentangle reductions in weed recruitment attributable to granivores from those due to plant competition. Using common lambsquarters as a focal weed species, we used experimental seed subsidies and differential seed predator exclusion to evaluate the utility of vertebrate and invertebrate seed predators in fallow, killed cover crop, and living mulch systems. Over two growing seasons, we found that seed predators were responsible for a 38% reduction in seedling emergence and 81% reduction in weed biomass in fallow plots following simulated seed rain, suggesting that granivory indeed overcomes safe-site limitation and suppresses weeds. However, the common lambsquarters densities in ambient seedbanks across fallow and cover crop treatments were high, and seed predators did not impact their abundance. Across the study, we found either neutral or negative effects of vertebrate seed predators on seed predation, suggesting that invertebrate seed predators contribute most to common lamnsquarters regulation in our system. These results imply that weed seed biocontrol by invertebrates can reduce propagule pressure initially following senescence, but other tools must be leveraged for long-term seedbank management.

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Amelioration of soil compaction by a cover-crop for no-tillage lettuce production

Australian Journal of Agricultural Research ◽

10.1071/ar9950553 ◽

1995 ◽

Vol 46 (3) ◽

pp. 553 ◽

Cited By ~ 17

Author(s):

RJ Stirzaker ◽

I White

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Sandy Loam ◽

Subterranean Clover ◽

Soil Surface ◽

Trifolium Subterraneum ◽

Field Trials ◽

Early Summer ◽

No Tillage ◽

Hot Weather

Excessive cultivation in many horticultural areas results in soil structural decline and poor utilization of water and nutrients. There are no reliable techniques for growing irrigated vegetables without cultivation. This work explores the hypothesis that a winter legume cover-crop can overcome the soil limitations of no-tillage and provide an alternative to excessive cultivation in the vegetable industry. We grew lettuce (Lactuca sativa) under no-tillage in field trials on a sandy loam soil following a bare winter fallow or a cover-crop of subterranean clover (Trifolium subterraneum), and compared this with cultivation by rotary hoe. The clover died naturally in early summer or was desiccated in the spring to form a mulch of at least 5 t ha-1 on the soil surface. The experiment was carried out over a 2.5 year period. The first crop was grown during hot weather and the soil in the no-tillage treatments was only moderately compacted. The yield of lettuce was similar in the no-tillage and cultivated treatments, and increased by about 30% when a mulch was added to each treatment. The soil was artificially compacted after the first crop. The second crop was grown 18 months later, during cooler spring weather, and following two further cover-crops. The yield of no-tillage lettuce was only 40% of that obtained with cultivation. Yield in the no-tillage treatment was doubled in two different ways: (1) by the addition of a surface mulch, and (2) through changes to soil structure stimulated by a cover-crop in the absence of a mulch. The experiments showed that a well-managed cover-crop can significantly ameliorate a compacted sandy soil by modifying soil temperature, soil strength, and by stimulating the formation of biopores.

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COVER CROPS IN THE OFF-SEASON IN THE WEED MANAGEMENT AT NOTILLAGE AREA

Revista Caatinga ◽

10.1590/1983-21252021v34n106rc ◽

2021 ◽

Vol 34 (1) ◽

pp. 50-57

Author(s):

FERNANDO COUTO DE ARAÚJO ◽

ADRIANO STEPHAN NASCENTE ◽

JULIANA LOURENÇO NUNES GUIMARÃES ◽

VINÍCIUS SILVA SOUSA ◽

MARCO ANTÔNIO MOREIRA DE FREITAS ◽

...

Keyword(s):

Cover Crops ◽

Weed Management ◽

Cover Crop ◽

Dry Matter ◽

Pennisetum Glaucum ◽

Pigeon Pea ◽

Weed Species ◽

Agricultural Areas ◽

Main Growth ◽

Crotalaria Spectabilis

ABSTRACT Cover crops can provide suppression of weeds and together with chemical control make the proper management of weeds in agricultural areas. The objective of this study was to evaluate the effect of cover crop cultivation during the off-season on weed development in a no-tillage area. The experimental design was in randomized blocks scheme with six treatments and four replications. The treatments were: fallow (control), millet (Pennisetum glaucum) + crotalaria (Crotalaria spectabilis + C. juncea + C. ochroleuca), millet + pigeon pea (Cajanus cajans), millet + Urochloa ruziziensis, millet + Urochloa ruziziensis + pigeon pea and millet + buckwheat (Fagopyrum esculentum. The evaluations were done at 30, 75 and 225 days after sowing of the cover crops (DAS). The main growth weed species in the area were Cenchrus echinathus, Euphorbia heterophylla and Digitaria insularis. Fallow treatment showed greater number of weed species with density of 184 plants m-2, 9.0 species and with 527.8 g m-2 of dry matter mass at 225 DAS. In all treatments verified reduction in the density and mass of weeds dry matter compared to the fallow, with average of 30 plants m-2, 5.8 species and 7.9 g m-2 at 225 DAS, respectively. The use of cover crops is an important strategy for weed control in agricultural areas.

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798 PB 074 CHANGES IN WEED SPECIES WITH DIFFERENT COVER CROPS IN TWO CALIFORNIA VINEYARDS

HortScience ◽

10.21273/hortsci.29.5.547e ◽

1994 ◽

Vol 29 (5) ◽

pp. 547e-547

Author(s):

Clyde L. Elmore ◽

Scott Steinmaus ◽

Dean Donaldson

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Management Practice ◽

Subterranean Clover ◽

Weed Species ◽

Perennial Weed ◽

Annual Bluegrass ◽

Wild Mustard ◽

Field Bindweed ◽

Winter Annual

Cover crops are grown in vineyards for many reasons, including erosion control, maintaining organic matter and changing pest complexes. Changing a management practice from using resident vegetation as a cover to other planted cover crops will change the vineyard floor flora. The cover crops of `Olge' oat, `Olge' oat and purple vetch, and purple vetch alone were compared to resident vegetation as winter planted cover crops. The cover was harvested in April of each year and blown under the vine row; The cover crop remains were disked into the middles after mulching. Three varieties of subterranean clover were planted in the vine rows at each location in one-half of each of the cover crops. The winter annual weed species, black and wild mustard, common chickweed and annual bluegrass decreased in the inter-row areas. The perennial weed field bindweed increased in all cover crop treatments.

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MANAGEMENT OF COVER CROPS FOR WEED CONTROL BETWEEN PLASTIC MULCH IN PEPPERS (CAPSICUM ANNUUM)

HortScience ◽

10.21273/hortsci.28.4.257e ◽

1993 ◽

Vol 28 (4) ◽

pp. 257E-257

Author(s):

Francis X. Mangan ◽

Mary Jane Else ◽

Stephen J. Herbert

Keyword(s):

White Clover ◽

Cover Crops ◽

Cover Crop ◽

Lolium Multiflorum ◽

Field Research ◽

Soil Surface ◽

Winter Rye ◽

Weed Species ◽

Plastic Mulch ◽

Crop Species

Field research was conducted in Deerfield, Mass. to study the effects of different cover crop species seeded between plastic mulch on weed pressure and pepper yield. A complete fertilizer was applied before plastic was laid on Sept. 13, 1991. Two cover crop treatments were seeded Sept. 13, 1991: white clover (Trifolium repens) alone and hairy vetch (Vicia villosa) in combination with winter rye (Secale cereale). On May 27, 1992 the vetch and rye were mow-killed with the biomass left on the soil surface. Annual rye (Lolium multiflorum) was then seeded on the same day as the third cover crop treatment. The remaining two treatments were a weedy check and a hand-weeded check. Peppers were transplanted into the plastic on May 31. Both the annual rye and clover were mowed three times over the course of the experiment with the biomass left between the plastic mulch. The white clover and annual rye were much more competitive with weed species than the dead mulch of vetch and rye. The three cover crop treatments had pepper yields that were severely depressed compared to the hand-weeded treatment. Among the three cover crop treatments, only the annual rye yielded more peppers than the weedy check.

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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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