03/21/2023
After extensive research and heartache, I want to share my experience with aminopyralid herbicide contamination in compost. Last year I ordered a dump trailer load of compost from a local horse farm in northwest Arkansas to finish filling my brand new garden beds. I had labored months with nothing more than basic tools to level and fill these beds, start seeds and create the garden of my dreams.
Though I have grown things over my lifetime, I have never done anything like the extent of this project. I am relatively inexperienced compared to folks whom have been gardening for years. I spent months, probably years, researching and learning what and how to grow a vegetable garden. I asked many questions and filled my head with enough basic knowledge that I put plants in the ground. I fully expected to experience failures and have many learning experiences. I just never expected that the compost I used to fill my garden and grow my plants would cause them to not grow and / or grow with distorted curled leaves that never led to production of the fruits I wanted for my labor. I had never come across a warning about using compost from farms in all my previous research.
How can compost be bad for plants you ask? The simple answer is because it can be contaminated with herbicides. Aminopyralid herbicides like Grazon are sprayed on to hayfields to control broadleaf weeds. The animals consume the hay or grass and the herbicide passes through their digestive systems and remains in their manure. When that manure is composted that herbicides still remain intact in the compost. When you plant in the compost things that are affected by that herbicide will begin to grow and quickly start to show damage in the form of curled leaves and most won't grow more than a few inches tall depending on the level of contamination in the soil. The most affected plant families are nightshades like tomatoes.. peppers.. potatoes and eggplants and the legume family peas, beans etc. I have read where some people experience problems with lettuce, melons carrots and other root crops as well.
In my experience my tomatoes and peppers were the most affected. I also had trouble with a second planting of potatoes I tried to make in fall after amending another bed that was previously filled with a good compost with the affected compost. They sprouted and died within a few weeks... I blamed myself because other things were growing fine. I had so many cucumbers I still have jars of pickles! People told me the weather was harsh it was a weird year everyone was having problems etc. But they were wrong it was only the beds that contained the contaminated horse manure.
Here is the next problem aminopyralid herbicide contamination can last for years in the soil. In my research I came across accounts ranging from 30 days to as much as 10 years. Some people are attempting to correct the compost with biochar and activated charcoal but these treatments can actually rob the nitrogen from the compost that plants need to grow. Some people are growing cover crops of grasses and mushrooms to cleanse the contamination but that takes time.
I'm am now facing a few options... I can try and grow only vegetables like corn squash and cucumbers that aren't affected by aminopyralid herbicides. I can empty all the composted out of my garden and replace. Replacement is a daunting task as I have inadvertently, before I learning what I know now, topped off every single bed and mixed in the contaminated manure getting ready for spring. But I have 100s of seedlings in my garage already growing that I already know won't grow in my beds as they are now. I also obtained 40 cattle mineral buckets to add to my garden this year and I can plant some of the sensitive plants in there as I have not filled them yet but space is still a problem.
Today I am taking samples from all my beds and the remaining compost pile and testing them with beans and peas to see hiw bad the contamination still is. Wish me the resolve I need to work through the issue and may you learn from my experience to be wary that this could happen to you.
A picture of one of my damaged tomato plant from last year.
