Most Arlingtonians know that feeding your lawns and gardens with compost and mulch is good practice for maintaining a healthy yard and helping the environment. The benefits of using compost are plentiful:
- Diverts organic materials from incineration, which is a last resort disposal method.
- Adds organic matter and nutrients to soil.
- Reduces the need for pesticides.
- Reduces the need for fertilizers.
- Increases biological activity in the soil.
- Prevents soil erosion.
To promote these environmental benefits, the Solid Waste Bureau collects the County’s brush and leaves then processes them into leaf and wood mulch. Arlington residents can collect the mulch for free or it can be delivered for a fee.
Problems Arising Due to Persistent Herbicides & Pesticides
Some regions of the country have reported damage to vegetable and flower crops after applying compost and mulch that contained persistent pesticide or herbicide residues. Persistent herbicides can make their way into compost through leaf and yard debris. While most residual traces of herbicides typically breakdown in a compost pile in a matter of days, these particular compounds can be resistant for months or even years. Some alarms have also been raised regarding the potential for composting to affect groundwater quality. A common broadleaf weed herbicide named “2,4-D” has been detected in rural and urban streams and shallow groundwater at low concentrations.
To ensure the quality of County mulches, the County collected a series of samples this spring and had them tested. The first set were sent to Pacific Agricultural Laboratory where the Acid Herbicide testing protocol was applied. Of the 15 analytes evaluated, only trace amounts of weed herbicide “2,4-D” were detected. Additionally, mulch samples were sent to A&L Great Lakes Laboratories for testing under the Seal of Testing Assurance Program established by the U.S. Composting Council. Test results, which can be found online, indicate a high level of integrity and “vigor” suitable for plant growth and soil sustainability.
What Residents Can Do to Help
The Solid Waste Bureau will continue to monitor our mulch to ensure the quality is maintained. However, residents can do their part to help keep our mulch and compost free of harmful pesticides and herbicides by adhering to the following tips:
- Keep pesticide/herbicide use to a minimum.
In addition to potentially making their way into the County’s mulch and compost, repeated use of toxic chemicals may destroy the microbiotic life that exists to help maintain sustainable healthy soil.
- Control lawn weeds naturally.
Corn gluten, a nontoxic byproduct of corn processing, kills weed seedlings within days of application. It also adds nitrogen to the soil. It is 60% effective with the first application, but after several years, this method can provide as much as 90% weed control. Another organic weed control option is chelated iron, which can be used to treat broad- leaf weeds like dandelions, clover, thistle and more. The product overdoses weeds with iron but leaves the lawn unaffected.
- ‘Spot-treat’ weeds to minimize herbicide use.
Where only a few scattered broadleaf weeds such as dandelions are present, consider spot-treating individual weeds with household vinegar rather than applying herbicide over the entire lawn. Mix 5 parts white vinegar, 2 parts water, 1 part dish soap and apply with a hand pump sprayer.