using lawn clippings in homemade compost after weed'n'feed

[CarolynB]

We make our own compost, and we want our compost to remain organic. We try to maintain a completely organic yard, but the lawn weeds are getting the best of us. Trying to even partially keep up with the lawn weeds by hand is taking needed time away from my job and other responsibilities. We're considering using a pre-emergent weed deterrent and/or "weed 'n' feed" on the lawns (although we'll continue to pull weeds by hand elsewhere in the yard). However, we currently use the lawn clippings in our compost, and we're not sure how safe it would be to do that if we use the weed deterrent products on the lawns. (The compost is used for our vegetable plants, which we want to remain organic.) Can anyone tell us: 1) How much of a health risk would there be if we use lawn clippings in compost used on vegetables after using weed deterrent products on the lawns? 2) If there is an unacceptable health risk, how long after application would it take for the chemicals to dissipate enough that it would be safe to use the lawn clippings in the compost again? (Note: Removing the lawns is not an option, because we don't own the home where we live.)

[Newt]

The best way I can think of to fight weeds in a lawn is to feed the soil so the lawn grows thickly. Weeds are opportunistic. If the conditions are right for them they will take over. I would core aerate, topdress with compost and use corn gluten meal as a pre-emergent to stay organic. Here's some handy links.

Areate:
https://www.homeandgardenmakeover.com/lawnaeration.html
https://www.american-lawns.com/lawns/aeration.html

Corn gluten meal - the second site has the Material Safety Data Sheet (MSDS):
https://web.extension.uiuc.edu/greenline/i1295_384.html#3
https://www.bioscape.com/bioweed1.html
https://www.dirtdoctor.com/view_question.php?id=17

...we currently use the lawn clippings in our compost...The compost is used for our vegetable plants, which we want to remain organic.

If you put the treated clippings in your compost you will no longer have organic compost. Of course you would need to know what chemicals and their life in the grass and in the soil. If you are on a well then the chemicals could seep into your well water.

How much of a health risk would there be if we use lawn clippings in compost used on vegetables after using weed deterrent products on the lawns?

Saying how much of a risk exists would be subjective. It would be best to research what is in the particular product you intend to use and what the research says. Here's a couple of sites you can use to research pesticides. Note that herbicides, pesticides and fungicides are all referred to as pesticides at these sites. Look to the left for links at this first site to search for MSDS - Material Safety Data Sheets.
https://www.greenbook.net/
https://pmep.cce.cornell.edu/facts-slides-self/facts/gen-posaf-health.html
https://www.ipmofalaska.com/files/profiles.html
https://www.pesticideinfo.org/Index.html

You should also find this helpful.
https://www.uri.edu/ce/factsheets/sheets/herbicides.html
https://www.clark.wa.gov/recycle/documents/Safer_Yard.pdf
https://www.uri.edu/ce/factsheets/sheets/leasttoxic.html
https://www.dirtdoctor.com/view_org_research.php?id=5

2) If there is an unacceptable health risk, how long after application would it take for the chemicals to dissipate enough that it would be safe to use the lawn clippings in the compost again?

As you research each product you should find the life and half life info, especially at the MSDS sites. If you have any problems with it just lmk.

Newt

[CarolynB]

Thank you for all the information. I haven't had a chance yet to look up all the web information you referenced, but I'll do that as soon as possible.

[Newt]

Carolyn, you are so very welcome! Don't hesitate to ask more questions once you look at those sites.

Newt

[lefty317]

carolyn,

let me try to put you at ease, any "weed and feed" if used at the proper rate will be safe for pets and children to be on the lawn after 3 days or so. after being processed in the heat of a compost pile for months, even less so. the very miniscule amounts if any in the clippings after being processed by the plant (nitrogen is nitrogen, and the ammonium concentration of a synthetic fertilizer is less than what my neighbors dog used to deposit on my lawn) should be of no consequence.. while not organic in the most stringent of definitions, neither is the epson salts that so many of us use to feed our plants.

[Newt]

Lefty, I don't agree with using grass clippings that were treated with a weed and feed product in compost. This site has loads of info on fertilizers and compost and I probably should have included it.
https://www.watoxics.org/homes-and-gardens/fastfacts/fastfacts-fertilizer

When you click on 'The Hazards of Weed and Feed' there's some interesting info there.
https://www.watoxics.org/homes-and-gardens/fastfacts/fastfacts-fertilizer#leadandarsenicf

The Hazards of Weed and Feed

Weed and feed is a mixture of lawn fertilizer with weed killer, usually 2,4-D and related compounds. The problem with weed and feed is that it is designed to be applied to the entire lawn regardless of whether or not weeds are actually present. This encourages over use. For example, if 30% of your lawn is covered in weeds, 70% of a weed and feed application will be wasted, since the herbicides have no residual action. Since many people do not realize that weed and feed is a pesticide, they may be less inclined to read an follow label instructions. For example, did you know that it is illegal to apply weed and feed more than twice per year on the same site?

The herbicides in most weed and feed products are mobile in soils and are widely found as pollutants in local streams, according to the U.S. Geological Survey. In addition, 2,4-D is neurotoxic and may be a carcinogen according to some studies.

Weed control should be practiced only as needed, not every time you fertilize. Mechanical controls are preferable to protect health and the environment. If chemical controls are used, spot treatment should be utilized to minimize product use and resultant risks from direct exposure and track-in to the home on shoes and feet.

There is also the section on 'Coated Fertilizers versus Organic Fertilizers'.
https://www.watoxics.org/homes-and-gardens/fastfacts/fastfacts-fertilizer#coatedfertilizers

Coated Fertilizers versus Organic Fertilizers

Coated fertilizers are made with pellets that have a shell on the outside to control the release of nutrients. The fertilizer itself can be, and usually is, synthetic in nature. Organic fertilizers, on the other hand, are made of naturally occurring plant, animal, or mineral-based materials. Most organic fertilizers release their nutrients slowly, although some types of fish fertilizer are relatively water soluble. The choice may involve philosophical principles as well as good gardening practice. Either coated or organic fertilizers will provide slow, steady nutrients, but the nutrients in the organic fertilizer may be more likely to require bacterial action to release them, while the shell coating only needs water and heat. Using an organic fertilizer, then, helps to support the beneficial microbes that you want in your lawn or garden. In addition, organic fertilizers are usually made from renewable resources and do not contain materials manufactured from petroleum.

Lots of good info there.
Newt