Testing straw for herbicide - bean damage

Question: I bought two round bales and a bunch of square ones at a straw auction, and realized I needed to test for herbicides in it before I use it on my organic farm.  So we did two tests.  Test one has several (24) tomato plants in 6 4-packs.  Two 4-packs are controls and just got regular water.  Two 4-packs got water that we'd soaked straw from a round bale in.  Two 4-packs got water that we'd soaked straw from one of the square bales in.  A week and a half later, those plants all look the same, but they're all root-bound and not really growing.

For the other test, two weeks ago we made a depression in one square bale and one round bale, put in plant starter mix, and directly planted four black bean seeds.  Some of them germinated in the usual four or five days.  In the round bale, one bean actually grew some.  In the square bale, two beans grew some.  (Field planted beans were our control for this, and they look normal.)  The beans that came up at all in both bales have the same weirdly distorted shape for their first true leaves - a hard curl to one side and then stop.  That's not what we expected to see, so I'm wondering if this is herbicide or if black beans were a poor choice of plant for testing in a straw bale.  (Note that in the third picture, the one without my thumb for size reference, there are new sprouting wheat seedlings coming up pretty-as-you-please, but the beans haven't done anything in several days.)

responder: The Question Asker Replied July 12, 2023, 8:23 AM EDT
response: Bit of a confusing update.  As of the 11th, a week after the question, one of the two bean plants in the square bale has sprouted a lot of lovely regular bean leaves.  The other is still just sitting there.  Meanwhile, the formerly big but stunted bean plant in the round bale has withered and died.  I don't know much about the herbicides out there, but this suggests to me that the original stunting wasn't the result of an herbicide like grazon.  All of the bean plants stunted in the same way, but with one of the plants in the square bale now growing normally, it can't be a systemic herbicide, or that plant would get worse.,  Could this be residual glyphosate?  Or is there some other herbicide that could create a pattern like this?  At this point, we're calling the square bales usable, but planning to scrap the round bales.  They'll end up as decoys for a straw bale hunting blind I have, so not a total waste.

responder: Thanks,  Replied July 12, 2023, 11:08 AM EDT
response: I read your question and whenever you are trying to find out what kind of pesticide may have been used, you are literally trying to find a needle in a haystack. In order to say there was a residue of herbicide in the bales, you would need to test bales from a particular field. At this point, it's not clear that the bales even came from the same field, so there may or may not be a different management plan for the farm. When testing for herbicide residue, this can be very expensive compared to the cost of the straw bales.  A bioassay is a good testing method, however, your methods may not give you accurate results. There could be confounding factors that affect the results. MSU does not test for herbicide residue so you would be responsible for sending samples to a private lab to have the material tested. We can supply a list of labs if you would like. From a practical standpoint, it may be cheaper and quicker to find a reliable organic straw source that you can have confidence in.