Compost Pesticides and/or Herbicides Residual Herbicides Soil Improvement and/or preparation

Municipal-Compost – Manures – Should you use them?

Karen, a reader, asked several questions on the post, Compost What it is and Methods Used to Get it.  I think the questions are important and are asked sooner or later by almost every gardener.  Thus, I am addressing them in this post.

She is preparing a new area in her yard for planting. Here’s what she writes:

“I want to consider adding manure but not sure how to even do that. I have some horse farms not far from where I live, but do not know anything about these horses what they have eaten, or been medically treated with (does that make a difference). —–

We also have an extension location here in Orlando where I can get free compost, is there any reason why I cannot use this?”

To answer Karen:

Although I can’t tell anyone what decision to make about using municipal compost and manures that you have no personal knowledge of —– I can tell you what I would do and give you some facts and ask some questions that will help you make your decision.

The Philosophy that I use to Guide What I Do

I imagine a line dividing ok-to-use-for-organic-gardening and  not-ok-to-use-for-organic-gardening.

Rather than see how close I can get to the line, I see how far away from the line as I can stay.  In most cases that simple philosophy makes it easy to decide what to do.

Things to Think About

Clopyralid, the herbicide  – and picloram

Some years back there was a lot problem with an herbicide, Clopyralid. It remains harmful through the composting process.  It will kill plants for many years after the composting process.

It’s my understanding that although it was banned as a lawn herbicide — it’s use is still permitted on grass hay and some grain crops. Supposedly  — grasses and other things contaminated with clopyralid are not allowed in compost facilities. But enforcement is lax if not nil.

As far as I know picloram which is just as dangerous — is still in use!

If horses and other animals eat grass hay or grain crops that have been sprayed with clopyralid or picloram, it will remain in the manure —- even after the manure is composted.

And then came Imprelis  – (aminocyclopyrachlor)

Imprelis was suppose to be safer than earlier weed killers and was marketed to control weeds in recreational areas such as golf courses and sod farms.  This “safe” product killed trees all over the country.  I believe it was finally banned in August 2011.

Even before it was banned the US Composting Council warned that anything treated with this chemical should not be composted because it would kill flowers and vegetables that the compost was used on – for up to 4 years after it was used.  I wonder who enforced that and how many people ended up with that chemical in their compost and wondered why their plants died?

Some communities have recycled plant bins.  What goes in them (and ends up in the compost facility) is probably never checked.  Since the vast majority of folks are not organic — and considering the huge amount of chemicals that are used today — it would seem a safe assumption that things sprayed with all kinds of chemicals are going to get into the mix.

3 More

There are others that fall into the same class (pyridine carboxylic acids) with picloram and clopyralid. The 3 I know about are Aminophyralid, fluroxypry, and triclopyr.

More Harmful Chemicals to Come?

With the way the world has gone chemical crazy, I’m sure more examples like those above await us in the future.

Toss of a Coin

Unfortunately when you use compost from a municipal compost facility and when you obtain manure about which you know nothing — you have no way of knowing for sure what will happen.  Like tossing a coin, you have a 50/50 chance. You could end up with great stuff or you could end up with stuff that may be harmful.

How would you know for sure if the chemicals are rendered harmless through the composting process until you used the compost?

That’s the question.  And the other questions:

  • Can you get additional information?
  • Are you willing to take a chance without knowing for sure?
  • How close to the line are you willing to get?

Your chances could be better one way or the other if you have some information about how things are done at these places. All is questionable UNTIL you know the facts.

In most cases — but not all — I would think that the composting process on a large scale (like that of municipal composting facilities) — IF done properly — would be more than adequate to remove the majority of any harmful substances that will break down. (As I mentioned above picloram, clopyralid, and imprelis and others like them — are not rendered harmless in the composting process.)

Also, most plant diseases are destroyed if the compost is hot enough. (I mention this because diseased plants end up in these compost facilities.)

If you can visit the operation and ask questions it might help you make your decision.

  • Does your municipal operation do the composting themselves or do they contract it out to a private company.
  • Are the ingredients from residential yards? Or are they from commercial contributors? (Chemicals used by homeowners are more likely to break down in the compost process.  Those used by commercial contributors could be ones like Imprelis,  etc. that don’t break down.)
  • Is there any testing done to make sure the end result is free from harmful chemicals like picloram, heavy metals, and other pathogens?
  • Is there documentation that says it meets the requirements of the National Organic Program (NOP).

Although they’re the exception to the rule, I’ve read of some municipal facilities whose compost if OMRI (Organic Materials Review Institute) approved!


Although generally speaking horse manure is probably the safest to use —- it’s still imperative to know your source.

And when I say safe — I only say that because overall —  horses probably receive less antibiotics than most other farm animals.  And since antibiotics can persist in the soil and be taken up by your vegetables they are a concern.

(You would think this alone would be enough to stop most farmers from using sludge on their fields — since sludge contains just about everything you can imagine. For more about this — see my post A Readers Thoughts and Mine/ Some Facts to Consider about Scotts.)

In addition, parasites in the manure from horses being wormed can persist in cold manure.

If you’re looking for horse manure that is safe — a lot will depend on stable management.  Except for the basic over all concerns, I’m not sure I would  be knowledgeable enough to ask ALL the right questions to enable me to make the right decision about using the manure.

Raw Manure — And When is it NOT Raw?

Raw manure is NEVER a good idea.  There’s lots of information that recommends it being at least 6 months old before using it in your garden.  After some extensive research — you might be like me and decide never to use raw manure — EVER!

And did you know that all manure — no matter how long it’s been sitting —- is still considered “raw manure” unless it’s been properly composted according to high composting standards and has achieved temperatures of between 133 and 170 degrees.

The way of things

For thousands of years farmers used manure without hesitation and much to their benefit.  In a closed system — where you raised your own animals and did things according to the laws of good health and stewardship —- you could still use it on your crops without hesitation.

In today’s world — lots of improper things are done — and many of them by folks who consider the “wrong way” perfectly ok.  So you must know a lot about your source in order to protect your garden —– and thus protect the health of you and your family.

A test that might be Helpful:

Years ago I read of someone testing municipal compost to see if it contained picloram or clopyralid.  I don’t know if it would work for every harmful chemical, but it would certainly be worth a try if you end up with compost or manure from an unknown source.

This particular gardener planted a couple of beans or peas in a pot and let them germinate and grow a few days. Then she put a cup or so of the compost into a jar of water. (Picloram or clopyralid dissolves readily in water.)  Then she watered the plants.  If the plant lived — she used the compost in her garden.  If it died in a few days — she knew she had bad stuff.

I recently read about one fellow that uses this basic test for every bit of manure he obtains because he once had all his crops ruined by  residual herbicides. (To test he puts the manure in the jar of water rather than the compost.) Needless to say — after that experience — he’s very careful what he uses on his garden.

Final Thoughts

Each person has a slightly different situation.  Each of us has to make the decision about what we will use in our gardens and therefore take into our bodies.

My best advice is:

  • If there is any way possible to avoid using compost and manures that you know nothing about — I would choose to do so.
  • If you have enough information to know it’s safe —- go for it!


Related Posts for even more information:

Gardening – Keep it Simple Because it Is     (Karen, I think you’ll find this one encouraging.)

Compost-Mulch-Residual Herbicides/ What you Can do About Them in Your Garden  and

Residual Herbicides in Composts Part 1

Part 2


Organic gardening is easy, effective, efficient — and it’s a lot healthier.


All content including photos is copyrighted by  All Rights Reserved.


  • Theresa,

    Thank you for your quick and detailed answer to my questions. Not knowing for sure what has been used on the compost from the municipal composting center, I think that I am going to pass, even if I ask, I am not sure they will know.

    At this point I will continue to build my soil with veggie scraps, coffee grinds, leaves etc. Today when we went to our local farmers market two of the sellers were more then happy to provide me with over 20 lbs of veggies that they could no longer sell.

    I then stopped at my local retail market, the manager in the fruit department said that he did not have anything today, but if I wanted to come back in the morning he would have plenty of skins etc for me. I guess after all of this sits for awhile I can then till it in, the soil can only be better then when I started. PS My backyard neighbor left me two big bags of mulched leaves next to my garden today 🙂


  • Theresa,
    Very well-written, and such chilling information.

    I like how you try to stay away from that line, rather than see how close you can get.

    I talked to a farmer once who said that there is SOMETHING either preventative, or otherwise, that you could be giving your horse EVERY month – if you were that kind of farmer. The drug companies send him free calendars around this time of the year, with the reminders for dosing printed for each month.

    What about the brown grocery bags?

  • Glad the post helped you make the decision, Karen. I think you’ll do just fine. Sounds like you have a lot of “helping hands”.
    Keep me posted.

  • Yes, Sandra, it is chilling information. Unfortunately, there’s a lot of chilling information in today’s world.

    What exactly are you asking about the brown grocery bags?


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