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 –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 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: –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: –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