If you use manure in your garden, this may help you avoid what happened to us last summer in Larimer County, Colorado.

Horse owners and gardeners may be interested in the following. We are summer residents in Berthoud, CO, and spend the winters in Oracle, AZ, where we haven’t encountered this problem. Kathryn Brown 

If you use manure in your garden, this may help you avoid what happened to us last summer in Larimer County, Colorado. Judging by our crop failures, we must have bought some horse feed that had been grown in the presence of an ‘aminopyralid‘ herbicide. These products (Milestone is the brand name of a popular one) kill weeds, but not grasses, thus producing weed-free hay. Unfortunately, the treated hay holds onto that chemical. When fed to animals, it passes right through them without harm, but the herbicide remains in their manure and urine. An unbroken chain of herbicide can stretch from field, to hay bale, to manure pile, and thus into your garden. Anywhere the manure goes, herbicide goes. And it can last in soil for up to three years! Unless the only vegetables you care to grow are squash, melons, and cucumbers, take heed.

We first heard about this kind of herbicide poisoning when we began to investigate why our most recent garden refused to grow beans, peas, tomatoes, or potatoes. We learned that hay or straw from treated fields is supposed to carry warning labels, but that did not happen in our case. Since we bought several small batches in different places, we can’t pinpoint the source of our poisoned hay. But we do know that our manure is herbicidal. We fear that unlabeled hay might still be on the market, so we want to share our experience and issue a warning. Unless you are absolutely sure about the safety of every chemical used within the past three years where your hay was grown, yours could be the next failed garden.

Before you assume that manure is ready to use, you should test it. Fill some little pots with straight potting soil, and some others with half potting soil and half manure. Plant bean or pea seeds in the pots, and leave them on a sunny window sill. Don’t let water from one pot cross-contaminate the others. After the seeds sprout, effects of herbicide poisoning will show up in about three or four weeks, if they’re going to. Seedlings grown in uncontaminated soil will look normal, but ones grown in the presence of herbicide either won’t come up at all, or will have small, wrinkled leaves, clenched growing tips, and a stunted appearance. They may stay alive, but they won’t thrive, and in the garden, they won’t produce fruit.

We now know a lot more than we wanted to about hay production, herbicides, and their effects on food crops. We now run every bit of horse feed, straw, and manure through windowsill science experiments before we use them. It’s a pain, but it beats the disappointment of enduring another season without beans, peas, potatoes or tomatoes, not to mention poisoned dirt. And we sure don’t want to contaminate the soil in our newly-opened plot. We hope others can learn from our experience and continue to enjoy their gardens, free of unwanted consequences.

-Kathryn Brown

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