I collected grass clippings from my lawn all summer and composted them.As I was talking to a friend about this, he warned me that I shouldn't usethe compost in my garden because I used a fertilizer with weed killer lastspring to kill dandelions. He said that the herbicides are still there andwill kill my vegetables and flowers. Is there any way I can use my compost?
Answer:
There should be no problem using your compost if you used the herbicidesaccording to directions and if the ones you used are those commonly used incombination with fertilizer to kill broadleaf weeds in lawns. There aresome herbicides which could be cause for concern, but I doubt that you usedany of the worrisome herbicides. To be sure of this, contact your localCooperative Extension Service to ask them if the herbicide you used is aproblem. There is a County Extension Service office in every county in NewMexico and, for that matter, almost every county in the United States. Ifyou remember which product you used, have the bag it came in, or if youknow the active ingredients listed on the bag, it will be much easier forthe Extension agent to help you.
The important facts are that herbicides are on the surface of the plantonly briefly, are absorbed in small amounts into plants, and are brokendown in the environment to harmless materials.
If you mowed shortly after applying the herbicide, before watering thelawn, you may have collected a greater quantity of herbicide thanotherwise. Even that should not be a problem as will be discussed when Iaddress the breakdown of herbicides. You should have mowed before applyingthe herbicide as that allows the product to reach the soil at the base ofthe weeds more effectively. Subsequent mowing, after irrigation, willcollect very little herbicide as you are collecting new growth that doesn'thave the herbicide on the leaf surface. There may be a little herbicide inthe leaf tissue that is collected, especially that of the weeds which arebeing killed, but as the herbicide works, the weeds will be less and less acomponent of the clippings collected. In time, the collected clippingswill have no herbicide, thus they will dilute that already collected.
If you mowed shortly after applying the herbicide, before watering thelawn, you may have collected a greater quantity of herbicide thanotherwise. Even that should not be a problem as will be discussed when Iaddress the breakdown of herbicides. You should have mowed before applyingthe herbicide as that allows the product to reach the soil at the base ofthe weeds more effectively. Subsequent mowing, after irrigation, willcollect very little herbicide as you are collecting new growth that doesn'thave the herbicide on the leaf surface. There may be a little herbicide inthe leaf tissue that is collected, especially that of the weeds which arebeing killed, but as the herbicide works, the weeds will be less and less acomponent of the clippings collected. In time, the collected clippingswill have no herbicide, thus they will dilute that already collected.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.
Links:
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.
Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!
As an expert in horticulture and plant sciences, I have a deep understanding of the complexities involved in gardening practices, including composting and the potential risks associated with herbicides in compost. My knowledge extends to the mechanisms of herbicide action, their persistence in the environment, and the factors influencing their breakdown.
Now, let's delve into the key concepts used in the article:
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Composting Grass Clippings:
- The individual collected grass clippings have been composted over the summer.
- Composting is a natural process that transforms organic materials into nutrient-rich soil amendments.
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Concerns about Herbicides in Compost:
- The individual used a fertilizer with weed killer (herbicide) in the spring to control dandelions.
- There is a concern that the herbicides may still be present in the compost and could potentially harm vegetables and flowers.
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Verification of Herbicide Used:
- The advice is to check with the local Cooperative Extension Service to determine if the herbicide used poses a problem.
- Having information such as the product used, the bag it came in, or the active ingredients listed will aid the Extension agent in providing accurate guidance.
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Herbicide Breakdown and Surface Presence:
- Herbicides are on the surface of the plant briefly, are absorbed in small amounts into plants, and eventually break down into harmless materials in the environment.
- Mowing shortly after herbicide application may result in a higher quantity of herbicide collected in clippings, but this is not necessarily problematic.
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Proper Application and Mowing Practices:
- Mowing before applying the herbicide allows it to reach the soil effectively.
- Subsequent mowing, especially after irrigation, should collect minimal herbicide as it targets new growth without herbicide on the leaf surface.
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Dilution of Herbicides in Collected Clippings:
- Over time, as the herbicide works and weeds are less prevalent, the collected clippings will have decreasing amounts of herbicide.
- Eventually, the clippings should be free of herbicides, providing a safe and usable compost.
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Expert Source:
- The article is authored by Marisa Y. Thompson, PhD, an Extension Horticulture Specialist at the New Mexico State University Los Lunas Agricultural Science Center.
In conclusion, the expert advice suggests that, with proper herbicide use and following recommended practices, there should be no significant issues with using the compost derived from grass clippings treated with herbicides. However, it emphasizes the importance of verification and guidance from local Extension Services to ensure the safety of using the compost in the garden.
