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Organic Weed Management
Jim Shrefler, Extension Horticulturist
and
Merritt Taylor, Professor of
Agricultural Economics
Okl...
Watermelon Trial - June 27
Watermelon Trial - July 10
Organics and Weed Management
Is there a quick guide to organic weed
control?
Is it good to have weeds on your farm?
Do org...
Organics and Weed Management
Organic farming systems use
vegetation management to:
– Improve soil
– Prevent soil loss and ...
Organics and Weed Management
Organic farming systems use
vegetation management to:
– Improve soil
– Prevent soil loss and ...
Organics and Weed Management
Vegetation that is managed
may include:
– Intentionally planted annual and
perennial cover cr...
Perennial Weeds
May or may not have
abundant seed production
May survive the winter via
roots or rhizomes
May or may not b...
Annual Weeds
Generally produce
abundant seeds
May be cool or warm
season plants
Are adapted to disturbed
environments
Have...
Organic Weed Management
Practices
Various farm practices may
contribute to weed management
– Carefully timed planting of c...
Organic Vegetables in
USA South Central Plains
Weeds pose a big
challenge to all
growers
With organics,
normally manageabl...
Weed Control Methods for
Organic Vegetables
Prevention
Cultural / Management
Soil preparation
Exclusion
Mechanical
Pruning...
Prevention
Avoid Introducing new
weeds
– Organic mulches
– Manures
– Moving contaminated
equipment
– Irrigation water
– Mo...
Prevention
Watch for new weeds
that appear
– Do not allow them to go to
seed
– Seed may persist for many
years
– If perenn...
Cultural / Management
Allelopathy
Organisms that
release “chemicals”
that inhibit growth of
other organisms
May be while the plant
is alive or d...
Application
methods
Crop safety
Efficacy
Preemergence Weed Control
Corn Gluten Meal
Onions
Summer Squash

Soil Preparation
Use sound practices
that do not harm soil
Eliminating all “green”
can be a good starting
point
Exclusion
Barriers that
prevent weeds
from establishing
Plastic mulch
Landscape fabrics
Carpet scraps
Organic mulches
Mechanical
Cultivation, hoeing,
hand removal
Labor intensive
Proper equipment
makes a big difference!
Cultivation for Weed Control in
Organic Vegetables
For some crops, such as
cucurbits, cultivation has
limitations
Vining g...
Pruning / mowing / flaming
Anything the gets above
ground parts of weeds
– Grazing
– Flaming
– Mowing
– String trimmers
We...
Chemical
Synthetic chemicals are not allowed in
organics
– Glyphosate, 2,4-D, “Poast”
Natural weed control “chemicals” are...
Postemergence Herbicides for
Organics
Integrated Management
Opportunities
Rye – a common winter cover crop
Rye has been shown to suppress
germination / establishment of weeds
Various...
Objectives
Compare field preparation / planting
system practices for:
– Impact on squash productivity
– Weed incidence and...
Materials and Methods
2004
Soil – Bernow fine sandy loam
Field history
– 2 year fallow
– Abundant crabgrass and tumble pig...
Materials and Methods
2005
Divide field  3 planting dates
– May, June and July
Mow cover crop, prepare plots and plant
Tr...
Treatment Advance
Procedures
At Plant
Procedures
Conventional Mow, Rework Rototill
Black plastic M+R; Plastic Nothing
Stal...
Response Variables
Squash Yields:
– Impact on squash productivity
Number of marketable fruit
Weed incidence
– Annual weeds...
Squash Yields*
First Planting Date
0
20
40
60
80
conven plastic stale seedbed mow mow & burn shallow shallow &
burn
Fruitp...
Squash Yields*
Second Planting Date
0
40
80
120
160
conven plastic stale seedbed mow mow & burn shallow shallow &
burn
Fru...
Summary – Squash Yields
Plastic mulch best with May planting
Any tillage, especially at-planting tillage,
was better than ...
Crabgrass
First Planting Date
0
400
800
1200
1600
2000
conven plastic stale
seedbed
mow mow & burn shallow shallow &
burn
...
Crabgrass
Second Planting Date
0
400
800
1200
conven plastic stale
seedbed
mow mow & burn shallow shallow &
burn
2 weeks 4...
Crabgrass
Third Planting Date
0
100
200
300
400
conven plastic stale
seedbed
mow mow & burn shallow shallow &
burn
1 week ...
Summary – Crabgrass
Crabgrass response to treatments varied
with planting dates
For PD1 and PD2 – greatest early
emergence...
Conclusions
The optimum system may depend on
planting date
– Plastic always produced greater or comparable
yields
– Weed p...
Interesting results in 2005
Plastic mulch always best
with early planting
Weed control results varied
with dry (2006) and ...
In Summary
Learn your weeds
Strive to prevent new
weed infestations
Learn and apply good
management practices
When all els...
Organic Weed Management
Organic Weed Management
Organic Weed Management
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Organic Weed Management

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Presentation by Jim Shrefler for the July 2013 Horticulture Workshop for the Oklahoma Beginning Farmer and Rancher Program. Held at the Kerr Center for Sustainable Agriculture in Poteau, OK.

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Transcript of "Organic Weed Management"

  1. 1. Organic Weed Management Jim Shrefler, Extension Horticulturist and Merritt Taylor, Professor of Agricultural Economics Oklahoma Cooperative Extension Service
  2. 2. Watermelon Trial - June 27
  3. 3. Watermelon Trial - July 10
  4. 4. Organics and Weed Management Is there a quick guide to organic weed control? Is it good to have weeds on your farm? Do organic growers just need to learn to accept weeds? Is learning to control weeds an ongoing process? Will there ever be an “organic” Roundup?
  5. 5. Organics and Weed Management Organic farming systems use vegetation management to: – Improve soil – Prevent soil loss and degradation – Enable production of field crops, forage and produce
  6. 6. Organics and Weed Management Organic farming systems use vegetation management to: – Improve soil – Prevent soil loss and degradation – Enable production of field crops, forage and produce
  7. 7. Organics and Weed Management Vegetation that is managed may include: – Intentionally planted annual and perennial cover crops – Annual and perennial cash crops Forages; Small Fruits – Naturally occurring plant species May include many species Some may be considered “weeds” Annuals and Perennials
  8. 8. Perennial Weeds May or may not have abundant seed production May survive the winter via roots or rhizomes May or may not be woody plants Include grasses, broadleaf and sedges
  9. 9. Annual Weeds Generally produce abundant seeds May be cool or warm season plants Are adapted to disturbed environments Have varied life cycle durations Seed may persist for years
  10. 10. Organic Weed Management Practices Various farm practices may contribute to weed management – Carefully timed planting of cover crops – Prevention of the introduction of undesirable plant species or cultivars – Carefully timed planting of cash crops – Prevention and removal of undesirable weeds in cash crops
  11. 11. Organic Vegetables in USA South Central Plains Weeds pose a big challenge to all growers With organics, normally manageable issues   major concerns – e.g. annual grasses
  12. 12. Weed Control Methods for Organic Vegetables Prevention Cultural / Management Soil preparation Exclusion Mechanical Pruning / mowing / flaming Chemical Allelopathy
  13. 13. Prevention Avoid Introducing new weeds – Organic mulches – Manures – Moving contaminated equipment – Irrigation water – Moving soil
  14. 14. Prevention Watch for new weeds that appear – Do not allow them to go to seed – Seed may persist for many years – If perennial, watch for regrowth from vegetative propagules
  15. 15. Cultural / Management
  16. 16. Allelopathy Organisms that release “chemicals” that inhibit growth of other organisms May be while the plant is alive or during its decomposition Certain varieties of cereal rye are an example
  17. 17. Application methods Crop safety Efficacy Preemergence Weed Control Corn Gluten Meal Onions Summer Squash 
  18. 18. Soil Preparation Use sound practices that do not harm soil Eliminating all “green” can be a good starting point
  19. 19. Exclusion Barriers that prevent weeds from establishing Plastic mulch Landscape fabrics Carpet scraps Organic mulches
  20. 20. Mechanical Cultivation, hoeing, hand removal Labor intensive Proper equipment makes a big difference!
  21. 21. Cultivation for Weed Control in Organic Vegetables For some crops, such as cucurbits, cultivation has limitations Vining growth habit Shallow roots Wet soil conditions may preclude effective cultivation
  22. 22. Pruning / mowing / flaming Anything the gets above ground parts of weeds – Grazing – Flaming – Mowing – String trimmers We will see some examples later
  23. 23. Chemical Synthetic chemicals are not allowed in organics – Glyphosate, 2,4-D, “Poast” Natural weed control “chemicals” are being developed – Vinegar – Plant extracts, oils – These are “burn down” products – A natural “Roundup” is not yet available
  24. 24. Postemergence Herbicides for Organics
  25. 25. Integrated Management
  26. 26. Opportunities Rye – a common winter cover crop Rye has been shown to suppress germination / establishment of weeds Various practices could be used to establish vegetables following a rye cover crop
  27. 27. Objectives Compare field preparation / planting system practices for: – Impact on squash productivity – Weed incidence and removal costs Compare treatments for production cost / economic benefit relationships
  28. 28. Materials and Methods 2004 Soil – Bernow fine sandy loam Field history – 2 year fallow – Abundant crabgrass and tumble pigweed Soil test and apply nutrients with poultry litter in autumn Beds – 6 foot centers Sow „Elbon‟ Rye
  29. 29. Materials and Methods 2005 Divide field  3 planting dates – May, June and July Mow cover crop, prepare plots and plant Transplant Zucchini squash „Revenue‟ – Spacings: Rows 1.8 m and plants 0.77 m Drip irrigation Weeds – count and hand hoe Harvest squash over about 3 weeks
  30. 30. Treatment Advance Procedures At Plant Procedures Conventional Mow, Rework Rototill Black plastic M+R; Plastic Nothing Stale seedbed M+R Burn Mow M M Mow & Burn M M+Burn Shallow till M Till (2-5 cm) St & Burn M Till+Burn Treatments
  31. 31. Response Variables Squash Yields: – Impact on squash productivity Number of marketable fruit Weed incidence – Annual weeds Weed removal requirements – Hoeing time
  32. 32. Squash Yields* First Planting Date 0 20 40 60 80 conven plastic stale seedbed mow mow & burn shallow shallow & burn Fruitperplot * Harvest period of 3 weeks LSD (0.05)=15.4
  33. 33. Squash Yields* Second Planting Date 0 40 80 120 160 conven plastic stale seedbed mow mow & burn shallow shallow & burn Fruitperplot * Harvest period of 3 weeks LSD (0.05)=23.6
  34. 34. Summary – Squash Yields Plastic mulch best with May planting Any tillage, especially at-planting tillage, was better than no tillage with June and July plantings – * conventional and shallow tillage were comparable
  35. 35. Crabgrass First Planting Date 0 400 800 1200 1600 2000 conven plastic stale seedbed mow mow & burn shallow shallow & burn 3 weeks 5 weeks Plants/m2
  36. 36. Crabgrass Second Planting Date 0 400 800 1200 conven plastic stale seedbed mow mow & burn shallow shallow & burn 2 weeks 4 weeks Plants/m2
  37. 37. Crabgrass Third Planting Date 0 100 200 300 400 conven plastic stale seedbed mow mow & burn shallow shallow & burn 1 week 5 weeks Plants/m2
  38. 38. Summary – Crabgrass Crabgrass response to treatments varied with planting dates For PD1 and PD2 – greatest early emergence with conventional and/or stale seedbed PD3 – appreciable emergence in all except plastic and non tilled plots
  39. 39. Conclusions The optimum system may depend on planting date – Plastic always produced greater or comparable yields – Weed patterns will probably differ across dates Shallow and conventional tillage yields were comparable – Are there benefits to shallow tillage?
  40. 40. Interesting results in 2005 Plastic mulch always best with early planting Weed control results varied with dry (2006) and wet (2007) conditions Predictability as a weed control tactic is questionable Results Over 3 Years
  41. 41. In Summary Learn your weeds Strive to prevent new weed infestations Learn and apply good management practices When all else fails – Keep on Hoeing!
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