Will 2,4-D breakdown after injestion as feed then composting for a year

I am able to get some horse manure (as much as I want) and the stable owners say they use 2,4-D before harvesting the hay and feeding it to the horses.  

The piles are well composted and we have a hot and humid environment.

I did a bean test last year and the beans did great in a mix of manure and store bought potting mix.  The beans did not grow at all in the straight potting mix.  

I am wondering if the resulting 2,4-D is so well broken down that it is no longer measurable since the piles are at least a year old.

I will also mix some with wood chips and hot compost for next year.

Should I be concerned about using this manure  to top dress my vegetables and fruit trees?  

Thanks

For any chemistry happening in uncontrolled conditions, the rate of degradation is highly dependent on conditions. The half life in aerobic soils is days. In anaerobic conditions (pond sediment), more like a year. I  don't bring any organic matter onto my farm from any source, because I don't want to be adding toxic gick to my fields. My experience has been that even people that think they are clean are adding unknown toxins to their lawns/fields/horses/bodies.

I personally worry more about if my garden grows than making sure it is super organic. I would definitely use that horse manure if I had access to it.
The only concern I have ever had with manures is if it is not from my own animals. The owners might have dewormed them and the manure will then kill soil organisms until the dewormers work their way out of the animals system.
I think if you take that horse manure and compost it with woodchips for a year, it will make a great soil ammendment.

So any remaining 2,4-D would have A) passed through a horse, and B) survived a year in a compost pile. Based on the conditions you described, and this article from Oregon State University, it sounds like half-life of anything that made it through the horses would be on the order of weeks. My guess would be at this point the amount of 2,4-D toxic gick in the compost is trivial compared to the toxic gick from other sources (rain, dust blown in, etc.). For one great example of how much stuff moves around, just think about the dust from the Sahara desert that fertilizes the Amazon rain forest.

As long as it's only 2,4-D you should be okay with it passing through horses and then composting. But if by any chance they had sprayed other herbicides of the aminopyralids class, those can continue to kill lots of garden vegetables even after passing through an herbivore and the resulting manure being composted for over a year. Terrible, terrifying stuff.

Rebecca Norman wrote:As long as it's only 2,4-D you should be okay with it passing through horses and then composting. But if by any chance they had sprayed other herbicides of the aminopyralids class, those can continue to kill lots of garden vegetables even after passing through an herbivore and the resulting manure being composted for over a year. Terrible, terrifying stuff.

For a little more aminopyralids reading check out
https://www.theguardian.com/environment/2008/jun/29/food.agriculture

I dug into the compost pile where I had made it from the horse manure last year.  Full of earth worms which I take is the best sign.