Safety of using soil from old horse barn?

I moved to my current place a couple of years ago and it had one previous owner, who's relatives built the place for them. It includes a cinderblock barn with wood rafters and a metal roof, a great outbuilding they used for horses. They stopped keeping horses years before selling, but the barn has been left more or less as-is, except we can see the wooden stalls they had attached to the walls within the barn were removed at some point.

The floor of the barn is just soil, uneven and built up toward the back where the horse stalls would've been. We want to put floors into part of it and will be excavating and leveling out the soil that's there. What can I do with this fill? There are some garden beds I'd be happy to build up with it, but I'm wondering about its safety.

Is there anything I should be concerned about, or any ways to test it for contaminants, before plopping it onto garden beds? We try to grow organic equivalent but are just growing for home and neighbors, not commercially organic. I am pretty paranoid about paint, plastic junk, livestock pharmaceuticals, etc. But it seems like after 5-10 or more years, pharmaceuticals from horses would degrade into less worrisome compounds, and I have no reason to believe the building itself would contaminate this soil given its made out of such inert materials. There's some plastic junk in the soil here and there but even premium organic compost ends up having microlitter in it.

What do you think?

Hm! Good question. I'm trying to think of "gotchas" in this situation but to be honest I can't think of any. Maybe folks with more horse knowledge can chime in.

Personally I would be inclined to muck it out and use it. If I had lingering doubts, I would add it to a limited space for the first season just to observe the results.

Here is a simple test:

Skandi said, Beans are very susceptible to this herbicide so the best and cheapest way to check for it is to sprout beans in the manure.

https://permies.com/t/139615/Residual-chemicals-horse-manure#1094446

If the previous owners were meticulous about their horses, they kept the stalls mucked out, so the floor is probably just dirt. I liked the advice above to do some experiments and see if anything grows in it. Good luck, I hope it has some fertility in it.

j

Thanks everyone. Sounds good to use it in a test bed or two, seeing how beans grow in it. I'll go ahead and try that! I guess if the beans grow well, I'll take that as a good sign to enjoy the beans and keep working with the soil.

I'd get a soil test that does heavy metals, if there is such a thing, or see if your local Ag agent does tests.