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Organic Weed Management

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Organic Weed Management Alisha Rupple, University of Arkansas Heather Friedrich, University of Arkansas * * Weed management is a top issue for most organic growers. – PowerPoint PPT presentation

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Title: Organic Weed Management


1
Organic Weed Management
Alisha Rupple, University of Arkansas Heather
Friedrich, University of Arkansas
2
Weeds Top Issue for Organic Farmers
  • Successful Management Requires
  • Multiple approaches
  • Continual effort
  • Knowledge of the biology of weeds species
  • Reproduction, lifecycle, establishment annual,
    perennial, wandering perennial, broadleaf, grass
  • Cornell Organic Weed Database, www.css.cornell.edu
    /WeedEco/WeedDatabase/index2.html

3
Basic Weed Ecology
  • Weeds are natures way of keeping bare ground
    covered and increasing biodiversity
  • Dynamic system involving the interaction of
    weeds, crops, humans and environment
  • Factors affecting weed ecology are identical to
    those affecting crop ecology
  • Light, temperature, water, pH, nutrients, organic
    matter, insects and diseases, etc

4
Impact of High Weed Pressure
  • Compete with crops for nutrients, water, and
    light
  • Reduced yields
  • Lower crop quality
  • Harbor pest insects and diseases
  • Increase irrigation costs
  • But, complete elimination of weeds is unnecessary

Crop yield
Weed numbers or size
5
Multiple Prevention and Elimination Strategies
  • Cultural
  • Mechanical
  • Biological
  • Chemical (organically
  • approved)

Many hammers approach. Liebman and Gallandt,
1997
6
Organic weed management practices Crop
Rotations on Organic Farms, Mohler Johnson, 2009
7
Cultural Strategies
  • Buy quality crop seed with low/no weed seeds
    present
  • Do not allow weeds to form seed
  • Thoroughly compost (gt130F for 15 days) all
    manure and plant residues to ensure destruction
    of weed seed
  • Stale seedbed technique
  • Prepare soil for planting and bring weed seeds to
    the surface allow weeds to germinate, kill weeds
    with light tillage/minimal soil disruption. May
    be repeated. Plant main crop.

8
Cultural Practices
  • Improve crop competitiveness
  • Improve soil tilth, aeration, and fertility to
    optimize crop growth
  • Increase crop density through narrow
    row spacing and increased seeding
    rate
  • Use transplants, rather than seed, when possible
  • Plant at optimal soil temperatures to prevent
    slow germination of crop
  • Choose competitive crop cultivars
  • Manage fertility according to crop needs avoid
    excess application

9
Cultural Practices
  • Reduce weed numbers
  • Mulch (wood chips, mow and blow, paper, living,
    plastic, etc)
  • Use weed-suppressive cover crops
  • Quick germinating, high biomass
  • Field with high weed pressure may warrant full
    year of cover cropping and fallow to reduce weeds
  • Crop rotations
  • altering narrowly spaced crops with closely
    spaced crops, shallow rooted/deep rooted crops,
    cold/warm season crops
  • Intercrop
  • Clover underseeded in sweetcorn

10
Mulch
  • Prevent seeds from germinating by blocking light,
    can smother out some weeds
  • Conserve water, minimal soil disruption
  • Use local resources straw, fabric, wood,
    newspaper, plastic
  • Be careful of weed seeds in straw or hay
  • Avoid hay, unless you know its free of weeds
  • Especially good for perennial systems
    blueberries, blackberries, flowers, trees
  • Living mulches ie constant cover of clover on
    orchard floor

11
Wood chips
Leaves
Shredded paper
Straw
12
Cover Crops
  • Smother weeds by out-competing for light, water,
    nutrients
  • Release allelopathic chemicals that suppress weed
    germination
  • May reduce weed emergence by 75-90
  • e.g. sudan grass, buckwheat, annual rye grass,
    sesbania, many more

Field pea-oat-mustard cover crop
Managing Cover Crops Profitably, 3rd ed. SARE
www.sare.org/publications/covercrops/covercrops.pd
f crops profitably. 3rd ed. SARE
Red Clover
13
Crop Rotations
  • Weeds tend to infest crops with similar life
    cycles
  • Change crop ecology shallow/deep roots,
    cold/warm season, row/drilled crops, foliage
    density, and heavy/light feeders
  • Change cultural practices cultivation, mowing,
    fertilization, herbicide application, and
    planting/harvest dates

14
10 Year Rotation SchemeAlex and Betsy Hitt,
Chapel Hill NC http//www.ssawg.org/hitt.html
15
Physical and Mechanical Practices
  • Mowing
  • Prevents seeding
  • Depletes storage reserves
  • Better control for broadleaves
  • Soil solarization
  • Effective control of winter annuals
  • Limited control of perennials
  • Cost prohibitive on large acreages
  • Avoid tillage deeper than 3 after solarization
  • Hand weeding
  • Cultivation
  • Flaming

16
Cultivation
  • Should be shallow to lessen disturbance to weed
    seed bank
  • Better for perennial and biennial control than
    annual weed control
  • Exhaust root system by depleting storage reserves
  • Requires 6-8 timely treatments in yr 1, then 3-5
    the following year

Wheel hoe
Thoroughly clean equipment before moving it
between fields to prevent weed transport
Various hoes
17
Potential Downsides of Cultivation
  • Exposes bare ground
  • increased erosion,
  • decreased biodiversity,
  • speeds decomposition of OM,
  • increases water run-off
  • Major cause of soil compaction
  • Cost expensive equipment, fuel
  • Should not be done in wet conditions

18
Use Cultivation Wisely
  • USDA-ARS research showed organic methods can
    increase OM more than conventional no-till
  • Teasdale et al., 2007. Potential Long-Term
    Benefits of No-Tillage and Organic Cropping
    Systems for Grain Production and Soil
    Improvement. Agron J. 991297-1305
  • Negative effects of tillage may be offset by the
    use of cover crops and additions of organic
    matter (compost, manures, mulch, etc)
  • Must still use caution to avoid negative effects
    of cultivation

19
Type of Horticultural Cultivators
  • Spyders
  • Torsion weeders
  • Spring hoe weeders
  • Finger weeder
  • Basket weeder
  • Multiple-component weeder frame
  • Brush weeder
  • Rotary tilling cultivators
  • Rear- or front-tine tillers
  • Hand implements push-pull hoes, hand scrapers,
    etc

Sustainable Vegetable Production from Start-Up to
Market, Grubinger, 1999
20
Other Cultivators
Sustainable Vegetable Production from Start-Up to
Market, Grubinger 1999, NRAES 104
21
Flaming
  • Intense heat sears the leaf, causing the cell sap
    to expand and disrupt cell walls
  • seedlings are most susceptible
  • Broadleaf weeds are more susceptible than grasses
  • May be used in wet soil conditions
  • VIDEO www.extension.org/pages/Video_Clip_Backpac
    k_Flame_Weeder_from_Vegetable_Farmers_and_their_We
    ed_Control_Machines

Sustainable Vegetable Production from Start-Up to
Market, Grubinger, 1999
22
Uses for Flaming
  • Stale seedbed technique
  • Planting delayed after seed bed preparation
    (tillage, irrigation, etc)
  • Flaming knockdowns flush of weed seedlings prior
    to planting
  • Peak emergence technique
  • Crop seeded promptly after seedbed preparation
  • Just before crop germinates, flaming used to kill
    weed seedlings
  • Good method for direct-seeded, slow-germinating
    crops
  • Glass or plastic can be used as a
    crop-germination indicator crop grown under
    cover germinates 2-3 days before uncovered crop
    flaming should occur when crop germinates under
    cover
  • Post-emergent flaming
  • Emerged crops protected by directing flame away
    from crops, shielding the crop, or flaming at a
    time when crop stems are resistant to heat
  • Older plants able to recover from heat damage,
    while young seedlings are killed

23
Flaming Tips
  • Bigger weeds and wet weeds are harder to kill
  • Target weeds while seedlings up to 3 to 4 leaves
  • Avoid flaming with morning dew
  • Light drying winds and hot days increase
    effectiveness
  • Avoid flame deflection by soil clods or excessive
    dust protect weeds
  • Match equipment for your needs
  • Save on fuel, time
  • Make time for adjustments
  • Burner placement, fuel pressure, tractor speed
  • How much is enough?
  • When you squeeze plant leaf between finger and
    thumb, want to see your thumb imprint cells
    have burst and weed will die/setback

24
Biological Control Practices
  • Insects may consume large numbers of weed seeds
    or feeding injury to plant or vector virus
  • Thistle adult thistle-head weevil, Rhinocyllus
    conicus
  • Multiflora rose rose rosette disease
    transmitted by fungi or a (mite)
  • Selective grazing
  • Sheep clean fields after harvest
  • Weeder geese useful against grass weeds and in
    perennial systems
  • Biofumigation
  • Use of Brassica species (canola, Indian mustard)
    as cover crop or in rotation
  • May be incorporated or left as residue
  • Brassicas produce glucosinolates, which may by
    converted to cyanate compounds during
    decomposition
  • Cyantes toxic to many bacteria, fungi, nematodes,
    insects, and germinating seeds

25
Chemical Control
  • Organic options
  • Corn gluten meal (pre-emergent herbicide)
  • Suppresses many common grasses and herbaceous
    weeds
  • WeedBan and Corn Weed Blocker
  • Look for non-gmo sources
  • Commonly based on vinegar or lemon juice or clove
    oil ingredients (post-emergent burndown
    herbicide)
  • Perennials may require multiple applications
  • Corrodes metal sprayer parts
  • Burnout, Bioganic, AllDown , MATRAN, and
    Weed Bye Bye
  • Post-emergent chemicals are phytotoxic (burn
    plant tissue) use caution when applying in crops

Organic herbicide in an orchard
Cost can be decreased by knowing pattern of weed
distribution (spot treatment v. overall
application
26
12 Steps to Sustainable Weed Management Mark
Schonbeck
  • Pre-season Planning
  • Step 1. Know the weeds on your farm.
  • Step 2. Plan cropping systems to minimize open
    niches for weeds.
  • Step 3. Keep the weeds guessing.
  • Step 4. Design the cropping system and select
    tools for effective weed control.

27
Preventive (Cultural) Practices
  • Step 5. Grow vigorous, competitive crops.
  • Step 6. Put the weeds out of work grow cover
    crops.
  • Step 7. Manage the weed seedbank minimize
    deposits and maximize withdrawls.

28
Control Tactics
Step 8. Knock the weeds out at critical times.
No-till organic farm Weed-free bed of
weed-sensitive onion crop.
  • Step 9. Utilize biological processes to enhance
    weed control.
  • Step 10. Bring existing weeds under control
    before planting weed-sensitive crops and
    long-term perennial crops.

29
Enhancing and Fine-tuning the Weed Management
Strategy
  • Step 11. Keep observing the weeds and adapt
    practices accordingly.
  • Keep notes
  • What is suitable for one crop may not be for
    another
  • Step 12. Experiment and stay educated. Keep up on
    new developments and practices.
  • Night time cultivation
  • Soil solarization
  • Others

Weed free bed of carrots
30
Conclusion
  • Using multiple approaches (many hammers) to
    manage weeds will yield greater impact than
    relying on a few practices.
  • Develop a weed management strategy that is
    designed for the needs of your farm.
  • Big Hammers
  • Competitive crops
  • Rotation
  • Cover Crops
  • Mulches
  • Weed predators
  • Livestock/grazers
  • Cultivation tools
  • Rollers/roller-crimper
  • Flamers
  • Growers Observation
  • Little Hammers
  • Solarization
  • Organic herbicides
  • Bioherbicides
  • Soil microorganisms
  • Crop-weed interactions

31
Resources
  • The Sustainable Weed Control Rag, Mark Schonbeck,
    e-Organic, www.extension.org/article/18529,
    www.extension.org/article/18539
  • www.extension.org/article/18538
  • Sustainable Vegetable Production from Start-up to
    Market, Grubinger, 1999. NRAES-104
  • Crop rotation on Organic Farms A Planning
    Manual, Mohler and Johnson, 2009. NRAES-177
  • Managing Cover Crops Profitably, 3rd ed. SARE
    www.sare.org/publications/covercrops/covercrops.pd
    f
  • Michigan Field Crop Pest Ecology Management.
    Cavigelli et al. 2000, MSU Extension Bulletin
    E-2704
  • Cornell Organic Weed Management Website,
    www.css.cornell.edu/WeedEco/WeedDatabase/index2.ht
    m l

32
Acknowledgements
  • This presentation address general organic
    production practices. It is to be to use in
    planning and conducting organic horticulture
    trainings. The presentation is part of project
    funded by a Southern SARE PDP titled Building
    Organic Agriculture Extension Training Capacity
    in the Southeast
  • Project Collaborators
  • Elena Garcia, University of Arkansas CESHeather
    Friedrich, University of ArkansasObadiah Njue,
    University of Arkansas at Pine BluffJeanine
    Davis, North Carolina State UniversityGeoff
    Zehnder, Clemson UniversityCharles Mitchell,
    Auburn UniversityRufina Ward, Alabama AM
    UniversityKen Ward, Alabama AM UniversityKaren
    Wynne, Alabama Sustainable Agriculture Network
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