We’ve been contemplating our soils since deciding to farm in Durango. We’ve had to; we’re farming in soil that made the bricks of an adobe house! Yes, clay soils have their pluses; they retain moisture (because it is dense), great for our dry climate. Plus, clay particles are negatively charged so they bind to positively charged cations that plants need (like calcium, magnesium, and potassium) so they are naturally very fertile. But, clay soils are slow to warm in the spring, and they are often alkaline which can limit the availability of micronutrients (our soil test indicated pH 8). My biggest challenge has been how easily they compact. Don’t even think about stepping on the soil and then trying to grow in it!

If you’re an organic gardener, you know the solution to everything is OM: organic matter. This is the best remedy for clay soils too. And I don’t mean a light spreading of an entire year of kitchen scraps that finally produced a pail full of compost; I mean 8 inches covering every inch of garden space! And that’s just to get started. Every time we rotate out a crop, we add more.

Where do you find all this OM and what is the best source? Sit back and pour yourself a cup of tea, I have quite a story to tell.

I spent the first fall that we lived in Durango driving around in my truck picking up OM. I investigated “hay for sale” signs and posted ads in the newspaper and on Craig’s list for moldy hay. On one of my drives, I came across a giant black pile of completely composted horse manure: “black gold”. I poked around the farm until I found the owner, a petite farmer sporting a huge cowboy hat. The pile was at least six years old and nothing new had been added since. Jackpot!! I jumped for joy and asked if I could load it in my truck with a shovel. He looked at me like I was either crazy or stupid and turned around to get his tractor. Last February with the greenhouse half finished, I started tomato seedlings in my window with the black gold. The plants barely germinated and those that did died a few weeks later. Too “hot” is what gardeners call manure that “burns” plants because it hasn’t completely composted and still has too much nitrogen.

But, this didn’t make a whole lot of sense considering the pile was 6 years old; for my Masters research I planted 1600 tomato plants with a shovel full of fresh cow manure placed in each planting hole. I puzzled on it for months and kept doing experiments in the greenhouse. The symptoms were distinctive. I’ve spent the better part of the last 10 years identifying tomato diseases and the epidemiology didn’t fit a pathogen. Something was the matter with this soil. It wasn’t until the local extension agent sent me this bulletin produced by NCSU on herbicide carryover in hay, manure, compost, and grass clippings that it started to click.

After pulling up images of herbicide damage on tomato, my heart sank. My preciously sought after OM was poisoned with herbicide. I guess it makes sense – a broadleaf herbicide is sprayed on pasture to kill broadleaf weeds while sparing the grass. Tomatoes are broadleaf plants too. But wait, let me get this straight… a horse eats some hay or grass sprayed with this broadleaf herbicide, digests it, poops it out, the poop sits in a pile for six years, and the herbicide is still present!! This is an unusually long half life compared to the farm chemicals I had studied in grad school. Sure enough, even the company that produces the pyridine carboxylic acid class of broadleaf herbicides warns users about carryover. Dow Chemical ironically calls it aminopyralid stewardship.

How can you be an environmental steward when using a chemical that lasts for years in the environment? One application and prime farmland is ruined for certain types of production for years to come. In asking a specialist whether a crop grown with herbicide carryover was safe to eat, he replied “if zero residual is a person’s goal in eating, they would starve to death.” Was there ever a better statement for growing without the use of synthetic chemicals, including the use of chemical-free soil amendments? How little we know about the ramifications of our actions. If this type of contamination is present in crops that are grown using organic methods, just think about what we are eating in conventionally grown crops where standard practice is to spray multiple applications of herbicides, fertilizers, fungicides, bactericides, and insecticides, whether they are needed or not.Since the pyridine carboxylic acid class of broadleaf herbicides were released by Dow chemical in 2005, contamination of OM has been reported worldwide. In the UK, the aminopyralid containing broadleaf herbicides were temporarily banned in 2008, until relabeling was negotiated. It has taken the US a bit longer to catch on.

Only a few states have raised awareness on the issue and here in Colorado, Milestone (an aminopyralid containing herbicide) seems to be everyone’s best friend. Until it is banned, canceled CSA’s and ruined home gardens will be the norm.

To me, this is local, national, and world headline news. What is more important than food security? I understand invasive weeds and those that are toxic to cattle are a problem. Proper pasture management, including intensive rotational grazing largely mitigates the need for herbicides, and if necessary, flame weeding is a better choice.

Oh yeah, back to my OM problem…your tea is probably gone. We’re now using wood chips, coffee grounds, leaves, needles, and manure that is from animals fed with certified organic hay. Let’s hope it doesn’t contain herbicide drift from the neighbor’s pasture! Adobe House Farm is lucky that the damage was largely to our seedlings which we were able to start again. We still had a bumper crop of tomatoes last year, which is one of the most sensitive crops. If this happens to you, irrigation, and rototilling (which exposes the compound to UV and oxygen) will help break it down. Please help spread the word that there are alternatives to using pyridine carboxylic acid containing herbicides.