Mulching & Other Methods for Weed Control

1. 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

2. 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

3. How Weeds Harm Desirable Plants • Competes for water, nutrients, light, and space • Harbors pests and diseases • Can release toxins into the soil

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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

10. Chicken Tractor • Mobile Pens • Weeding • Pest Control • Fertilizer • Food

11. 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

12. 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

13. 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

14. 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

15. 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

16. Palm fronds around breadfruit tree

17. 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

18. Mulched Raised Bed • Bed mulched with pine needles (Gago tree)

19. 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

20. Undesirable - Mulch up Against Trunk

21. 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.

22. 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

23. Wire Chicken Barrier

24. Possible Problems • Chickens and Pigs love it too • Can destroy plants, dig up roots • Scatter mulch • Where animals are a pest, create a barrier