Transcript Organics - Guam Sustainable Agriculture Resource Page

Mulching & Other
Methods for Weed Control
Prepared by:
L. Robert Barber, Frank Cruz, & Ilene Iriarte
For:
Guam Cooperative Extension Service & Guam Department of
Agriculture
Funding provided by:
United States Department of Agriculture Natural Resources
Conservation Service, Western Region Sustainable Agriculture
Research and Education, Administration for Native Americans,, &
Sanctuary Incorporated
What is a weed?
• Plant growing out of place
• A plant can be desirable in one situation
and be a pest in another
– Can be fast growing
– Often produces a lot of seeds or has persistent
roots
How Weeds Harm Desirable Plants
• Competes for water, nutrients, light, and
space
• Harbors pests and diseases
• Can release toxins into the soil
Weed Management
• The best time to begin an effective weed
management program is before planting
• Proper site preparation can reduce weed
problems
• Monitor frequently for weeds
• Remove weeds while they’re seedlings
• Maintain a directed low volume irrigation
system
• Minimize disturbances in the soil
• Correctly maintain mulch
Weed Control Practices
• Mechanical
– Hoeing/Hand weeding
– Plowing, harrowing, cultivating, other tillage
• Fire/Propane Burner
• Mowing/Bush cutting
• Ground Cover – Living Mulches
• Chicken Tractor
• Mulching
Mechanical Weeding - Cultivation
• Labor, equipment and energy intensive
• Bare soil more susceptible to erosion
• Frequent tillage speeds organic matter
decomposition.
• Brings buried seeds to the surface
– Cultivate once germinated
• Plant spacing must allow for equipment
Fire
• Fire can be used to remove weeds in a big
area
– Burns the organic matter
– Leaves soil bear and high chance of erosion
• Propane Burner is used for spot
treatments
– Must be careful
Mowing & Bush cutting
• Benefits of maintaining a living cover and
mowing or bush cutting
– May reduce competition
– Can help prevent soil erosion
• Disadvantages:
– Often damages desired plants
– Physically harms plants – Bush cutter disease
(careless cuts girdle tree) kills huge numbers
of trees on Guam.
Ground Covers or Living Mulches
• Can be natural cover developed by frequent
mowing, or can be planned planting like sweet
potato or perennial peanut or other cover crop.
• Benefits
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Prevents germination of weed seeds
Prevents soil erosion
Insulates soil
May add nitrogen to soil (ex. Perennial peanut)
Attractive
• Disadvantages
– Can provide a habitat for pests
– Can compete for water & nutrients
Chicken Tractor
• Mobile Pens
• Weeding
• Pest Control
• Fertilizer
• Food
Types of Mulch
• Two types of mulch; Organic & Inorganic
• Inorganic Mulch (Plastic sheets):
– Does not decompose
– Non-living
– May prevent water loss, soil protection,
increase absorption
– Does not improve soil or add nutrients
– Good for walk ways, and paths
Benefits of Mulch
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Conserves water & reduces erosion
Improves soil structure, & absorption
Adds nutrients
Suppress weed growth
Prevents pathogens from splashing on foliage
Insulates soil
Increases microorganisms, earthworms, & insects
Prevents trunk damage from bush cutter
– Limits weeds near plant so no need to cut close to plant
• Reduces landscape maintenance
Organic Mulch
• Organic Mulch:
– Living Materials
– Categorized by size; Fine or Coarse Material
– Fine Material:
• A lot of surface area
• Can suffocate plants
– Coarse Material:
• Doesn’t blow away as easily
• Water & air can penetrate through
Organic Mulch
• Examples of Organic Mulch:
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Grass clippings, small leaves*
Wood chips**
Pine needles (Gago Tree)**
Banana leaves & Palm fronds**
Coconut husks**
Branches**
Compost
Shredded paper*
*Fine Material & ** Coarse Material
What is in a Mulch
• Decaying organic material
• Undecomposed compost
• Applied to surface of the soil over time blends
with the soil
• Consists of:
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Nutrients
Leaves
Branches
Microorganisms
Insects

Palm fronds around breadfruit tree
Now That You Have Mulch
• Apply in planting beds
• Around established trees, & newly
planted trees
• Mulch will eventually need replacing
• Fine material need to be replaced often
• Coarse material can be replaced either
once a year to every two years
Mulched Raised Bed
Bed mulched with pine
needles (Gago tree)

How To Apply Mulch
• Leave a 3-6” gap from the base of the plant
to mulch
• For individual trees:
– Make a circle that is 2’ in diameter for every
inch of trunk diameter
– Increase size as tree gets bigger
• For planting beds:
– Mulch entire bed
Undesirable - Mulch up Against Trunk
How Much to Apply
• Thickness depends on types of material
• Fine Material:
– No thicker than 2 – 3 inches
– Can mat together & suffocate plants
• Coarse Material:
– At least 4 inches
– Thinner weeds can penetrate through if too
thin a layer.
Possible Problems
• Mulch can turn “sour”
– Air was not allowed to penetrate through
– Toxic substances are produced
– Plants drop leaves, turn yellow, and can die
– Smells like sulfur, vinegar, or ammonia
Wire Chicken Barrier
Possible Problems
• Chickens and Pigs love it too
– Can destroy plants, dig up roots
– Scatter mulch
– Where animals are a pest, create a barrier