Should I dig out herbicide-laced soil?

pipperee(6a / 6b eastern WA)August 19, 2013

We built new raised beds this year and filled them with truckfulls of purchase soil and compost. After much handwringing, hair pulling, and a few tears when I saw all my plants stunted, shriveling, dying, I determined through some different bioassays that herbicide contamination was the root of my problem.

Now I have to decide: dig out 3 beds and replace with new soil or try something else. I'm not worried about the cost as much as I am time and labor. I've seen some mention of using activated charcoal, but only in articles from 11yrs ago. Some articles suggest that nature alone will take care of it within a year, but other articles state it can remain several years. I don't want middling results, I want a healthy garden next year!

Does anyone have experience with successfully "healing" contaminated soil?

Just a sample of my results this summer: tomatoes, while stunted & bizarre looking, are producing a crop. Peas croaked. Cucumbers are barely surviving - I may get a few fruit. Onions are stunted ( although my first time growing, so that could be my error). Marigolds and dahlias have twisted, scorched leaves with few flowers. Thyme looks scorched. Peppers have had mixed success- some seemed to out grow the damage, others are stunted and not producing. Surprisingly, my lettuce and basil didn't seem
too bothered by it.

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First question - if you remove the contaminated soil, what will you do with it ? Think about this very carefully, because trying to dispose of it as waste potentially has a lot of legal issues.

    Bookmark   August 19, 2013 at 6:41AM
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pipperee(6a / 6b eastern WA)

Good question: as much as it pains me to throw dirt away, I can't in good conscious send it back to our compost facilities so I was thinking we'd just take it to the dump (ugh).

I hadn't considered legal issues: can you explain?

I just had another thought: it's supposed to be fine for grass, right? Perhaps I could just spread it thinly across the lawn (also not my favorite option since we have a chem-free lawn).

I guess the follow up question then, is what is the best disposal option, if that's the best solution?

    Bookmark   August 19, 2013 at 7:05AM
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Putting herbicide contaminated soil in a municipal dump might just land you in conflict with a bunch of Federal and possibly state disposal regulations, so I wouldn't go that route.

Spreading it across your lawn, as a top dressing, is a viable option, so long as you have a good idea of what the contaminant is (the most common is clopyralid).

As far as remediating the soil in place, I am not a fan of adsorption onto activated carbon. The preferred approach is to promote microbial degradation. See the link below for Green Mountain Composting in VT, where the problem became rather significant several years ago. To do that you want to keep the soil most, but not wet, and aerate and turn it somewhat frequently (at least monthly). You can likely hasten the process by adding some food for the microbial community, in the form of a clean carbon source along with adequate nitrogen to promote development. A good combination is clean hardwood mulch plus either urea (2 lbs per 100 lbs of mulch) or bloodmeal (6 lbs per 100 lbs of mulch). If you have a source of known clean compost, you could use that as well. Either way till it in, and keep turning.

In VT where the problem became significant they also found growing a late season cover crop of oats, then cutting and safely disposing of the oats helped.

Do you know where the contamination came from? If so, you might find some help from the supplier, but I wouldn't hold my breath. Some composters have been very dutiful in their help and support, while others have tried to sidestep any responsibility. You might also contact your local county extension agent to see if your state extension service has any knowledge or can provide any help.

In which state are you located?

Here is a link that might be useful: Recommendations for Accelerated Remediation of Persistent Herbicides

    Bookmark   August 19, 2013 at 7:44AM
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You might also look over the fact sheet from Green Mountain Compost linked below for some additional insight.

Also. be on the lookout for a reply from toxcrusadr - he's extremely knowledgeable on many of the regulatory issues issues (it's what he does for a living), as well as composting, etc.

Here is a link that might be useful: Compost & Persistent Herbicides Fact Sheet

This post was edited by TXEB on Mon, Aug 19, 13 at 8:01

    Bookmark   August 19, 2013 at 7:57AM
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pipperee(6a / 6b eastern WA)

Thank you for all the info!

I'm in WA; the eastern, semi-arid, non-Seattle side of the state.

Follow-up Question (which may be answered in your links that I will read this evening): since i got my soil from a facility that accepts waste from many sources I don't hold out hope that they will know. How can I determine which herbicide in particular is my problem?

    Bookmark   August 19, 2013 at 8:18AM
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You may be able to get more help than you realize. The entire clopyralid/ compost contamination issue originated in WA. See the link below for some more info, and definitely contact your county agent. In WA they may know more about it than about any other state.

Here is a link that might be useful: WSU - Clopyralid in Compost

    Bookmark   August 19, 2013 at 8:29AM
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In your situation, I would leave the soil where it is, and grow flowers in the new raised beds. Some will fail, some will do OK, so I would focus on planting the species that do well. Chances are the herbicide levels will be down to undetectable by 2015, and then you can plant what you want. The herbicides in your soil are not indestructible and they will break down, eventually.

    Bookmark   August 19, 2013 at 10:37AM
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This is another good reference pertinent to WA - I had this stashed in my files, but wanted to find the online reference. Here it is.

Here is a link that might be useful: WDA - Herbicides in compost

    Bookmark   August 19, 2013 at 11:27AM
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Edit to add: Whoops, I now see TXEB already covered going back to the supplier.

I'd inform the supplier that you are having problems. If they are reputable, they will want to investigate to determine the exact cause of the problem. Keep written documentation and a log of every time you talk to them including the persons name and subject of the conversation. Photographs of the plants and their problems would probably be helpful. I would not be surprised if they offered to remove the product if they felt you had a case against them. Getting a reputation as a supplier of contaminated soil/compost is something they would likely like to avoid if they are at all a good company.


This post was edited by pt03 on Mon, Aug 19, 13 at 12:00

    Bookmark   August 19, 2013 at 11:52AM
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toxcrusadr Clay Soil(Zone 6a - MO)

I agree. If the situation is ever going to change, it will be through strident complaints travelling upstream from the customer to the supplier to their suppliers! I recommend you moan and complain, politely of course, and make the soil vendor replace it. This will make them think twice about where they get their organic matter.

Now, as far as disposal, if it comes to that: I thought that "pesticides applied according to label instructions" were not considered a RCRA Hazardous Waste. If so the soil they are applied to cannot be hazardous waste either. Therefore a regular Subtitle D sanitary landfill could accept it. The most direct way to find out is to call the landfill. They have the last word on what they will accept. Make sure they understand it was not from a spill, but from persistent herbicides applied to hayfields.

This post was edited by toxcrusadr on Thu, Dec 12, 13 at 11:53

    Bookmark   August 19, 2013 at 12:39PM
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tox - I'm sure you're correct about the RCRA classification. However, given the problems WA had when this whole thing started, I'd want to know that they don't have state code regarding disposal of herbicide contaminated materials.

    Bookmark   August 19, 2013 at 12:54PM
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tishtoshnm Zone 6/NM

A couple years ago I added contaminated manure to my vegetable garden. Time really has been the best healer (but yeah, a couple of years, especially with our droughts). If I were in your shoes, I would add more compost this fall and again in the spring, do your best to get it the bed as active as possible. I would also irrigate it, irrigate it and irrigate it. Also, get a cover crop growing in it, oats would probably work well.

If it is clopyralid, it sounds like it is not the only problem though. Clopyralid would not affect cucurbits. In fact, my melons grown in that manure were fabulous. It could also have been too hot (not composted enough) when added. I truly understand your heartbreak and I hope that you eventually will get the garden of your dreams.

    Bookmark   August 19, 2013 at 2:48PM
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tishtosh brings up a good and valid point that I had missed in the OP - you may be suffering from persistent herbicide carryover, but you likely have other soil problems as well.

The usual and most common herbicide carryover problems have been with clopyralid, aminopyralid and picloram. The typical crops affected are solanaceae (tomatoes, peppers, eggplants) and legumes (beans, peas). The fact that your tomatoes and peppers while affected are producing, but your cucumbers are barely surviving suggests other issues (it's backwards from what would be expected for the herbicides I mentioned).

Some of the plant-related symptoms you described sound very similar to what I experienced this year in a new bed where I overdid the addition of composted manure and pushed the phosphorous to really excessive levels, which precluded the effective use of several essential micronutrients (especially iron and zinc). I'm not suggesting that is your problem, but it illustrates that plant nutrient levels in your soil may be as much of a problem as herbicide carryover.

I would encourage you to get a good soil test, including micronutrients and boron before you take any significant action on your garden soil. Unfortunately, WA doesn't have a state lab. But WSU does provide a listing of soil labs that serve the PNW (see link below). For what it's worth, I've heard positive things about A&L Western Laboratories ( ), and their fees are comparable to what I pay for testing by TAMU here in TX. If you decided to use them I would suggest their S1B + S3 analyses ($32 total with recommendations), or for $3 more get the S3C package which adds nitrate N plus soluble salts and excess lime. That testing may well save you well more than the cost in subsequent effort. If a good soil analysis comes back looking good, then you can focus on the possibility of herbicide carryover.

Here is a link that might be useful: WSU - Soil Testing Labs for the PNW

This post was edited by TXEB on Mon, Aug 19, 13 at 18:24

    Bookmark   August 19, 2013 at 4:37PM
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There are a number of greens you can grow in that soil. I know many of you feel lost without tomatoes but they are not that nutritious and have mildly toxic compounds. You can use the soil, even this year. But if you are betting the farm on next year, yes, thick cover crop (not favas), add very unfinished organic matter (wood chips and kitchen scraps, or fresh manure), and let it cook over the winter

    Bookmark   August 19, 2013 at 9:31PM
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tishtoshnm Zone 6/NM

If it is clopyralid, it is possible to still get tomatoes. I did but they were greatly deformed. The herbicides in that family also affect whatever family spinach is in.

But, for now you could grow brassicas, depending on your zone, that could be broccoli, cauliflower or if not enough time for those mustard greens, turnip greens, collards.

If you go the route of allowing time to take care of it, you could try tomatoes in pots next year. I did find that peppers and eggplants were less affected. Our dahlias seemed to be sensitive to the herbicide as well. Alliums seemed to be okay. Good luck.

    Bookmark   August 19, 2013 at 10:49PM
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david52 Zone 6

I'd be tempted to mix in lots of wood chips and organic matter and cover it with a clear plastic sheet - then let it cook.

    Bookmark   August 20, 2013 at 10:45AM
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Nothing wrong with the wood chips, provided you add enough of an N source to go with the C. Covering it and "letting it cook", though, is absolutely the wrong direction. The pyridine carboxylic acids decompose under aerobic conditions, and tend to be most persistent under anaerobic conditions. Aminopyralid in particular sticks around a very long time in stacked manure, but will decompose at a very reasonable rate if turned frequently.

    Bookmark   August 20, 2013 at 4:24PM
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I cannot believe that you are still finding herbicide-contaminated soil or compost anywhere in WA state!!

First, we were the first to discover problems with herbicide contaminated commercial or municipal compost and legislation went in to effect virtually immediately (2002) to restrict the use of persistent herbicides. Some eleven years later, it is difficult to imagine there is still a problem with this stuff. Second, most municipal/commercial compost processing operations have to go through testing to make sure their product is contaminate-free, so there is a bit of a double check here as well.

These products are still approved for agricultural use on some grain and hay crops so the risk of contaminated animal manures persists. If you live in WA state it is best to purchase compost or soils from reputable commercial vendors or municipal facilities to make sure you avoid the smaller, businesses that may not be so discerning in their product requirements (i.e., including potentially contaminated manures).

Because of the history of herbicide contaminated compost and associated publicity in our area and the restrictive controls surrounding it, I'd also surmise this is not your primary cause of the issues you describe. Before you go to the effort of removing and replacing all the soil in question, I would agree a good thorough soil test is in order. FWIW, you can also request to have the soil tested for the specific 3 contaminates TXEB listed (for an additional cost). These are the only truly persistent culprits - anything else should be mitigated with any OM rather rapidly.

    Bookmark   August 20, 2013 at 4:53PM
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gardengal - it is now rare, but there are occasional reports of contaminated garden products, most typically manures. The major problem of contaminated municipal composts was largely resolved when clopyralid was removed from use on residential tufgrass in 2002. However, all three of the aforementioned herbicides continue to be used in agriculture as well as state and municipal land management. As a result, there continue to be reports of contaminated manures. At one point it became enough of a problem or a concern in some areas of WI that manure from cows that had been fed on treated hays/grains was embargoed from export from their native farm (imagine the backup that created). There was one report from VT I believe in 2011 from compost contaminated via horse manure, where the herbicide came in via a major brand of commercial horse feed. As far as I know municipal compost streams are today pretty free from the problem, so long as they don't use animal manures. Private yards, however, who compost and sell manure products continue to have the periodic mishap, but it usually doesn't make it into the news circles.

BTW - the going rate on the cheap for analyses of the herbicides is $150/compound per sample. I am not sure, however, of how their detection limits are at those prices - it would need to be on the order of 1 ppb to be worthwhile.

    Bookmark   August 20, 2013 at 6:06PM
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pipperee(6a / 6b eastern WA)

Thanks so much for the suggestions and information ! before I contact my soil supplier I will get my soil tested to make sure there weren't other glaring issues.

Good to know that some commercial suppliers do extra testing. I went for the cheaper homegrown operation for my soil and compost this time and I think I got my money's worth!

    Bookmark   August 20, 2013 at 9:08PM
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Good plan! Do let us know what the soil analysis shows.

    Bookmark   August 20, 2013 at 9:16PM
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pipperee(6a / 6b eastern WA)

ItâÂÂs cold outside, so IâÂÂve got plenty of time to tell you how it all ended. I took in several samples of my Franken-plants to the Master Gardners. The pro in the office immediately said: âÂÂaminopyralid.â Apparently it was one of many cases sheâÂÂd seen this year and she said that it continues to be a problem, mainly from contaminated manure in compost. I had based most of my research on googling âÂÂclopyralidâ so when I did a new search, I immediately got a lot of hits showing that is still very much an issue in the Northwest (at least within the last couple of years). Sad. Also, I found the best pics yet of what the damage looks like - which is exactly what my tomatoes and peppers looked like (see link below).

So what did I decide on? Well, after all the work cutting the sod & building the beds in the only spot on our little city lot that has enough sun (no extra space even for pots), and being far too impatient to let it resolve over a few years (several seasons without produce after all that work?!) we decided to dig it out. We took it back to the supplier who returned our money. They were very gracious, and alarmed at our experience. We must have gotten a random bad batch as they themselves use it in their gardens, and some of my friends used it without trouble (although maybe not to completely fill new raised beds like I did).

Apparently there are some suppliers in the area that test for these chemicals, so we will try again next summer - I feel so fortunate that we can afford to! While it was sad to tear out all the produce (we opted not to eat any, regardless of what Big Chem says is safe), and frustrating to dig out all the dirt (gave up a beautiful fall weekend to do it), I just kept thinking of my grandparents who lost their farm after a couple of bad crops back in the early 1940âÂÂs and then had their one dairy cow die as they were moving their 8 kids to a rental. IâÂÂve got no room to complain!

Thanks for everyoneâÂÂs input, advice, ideas & experience.

Here is a link that might be useful: WSU Extension Aminopyralid Pictures

    Bookmark   December 11, 2013 at 4:46PM
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jean001a(Portland OR 7b)

And this page at WSU tells how to do a simple bio-assay on "new" composts, manure, or soil you acquire.

Also notice that info re helping the herbicide degrade is also available from WSU. Just takes a season/year, not several.

Oh yes.Thanks for the update. It's helpful to us to know the outcome.

Here is a link that might be useful: bioassay.

This post was edited by jean001a on Wed, Dec 11, 13 at 19:58

    Bookmark   December 11, 2013 at 7:57PM
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This is a scary experience. This is one of the reasons a lot of people recommend working with existing soil and improve over time.

    Bookmark   July 18, 2014 at 10:45PM
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