This is bothering me a bit. I doubt it's herbicide carryover because seedlings that sprout in contaminated soil can be deformed from the get go.

See images of bean seedlings from a university trial here: https://s3.wp.wsu.edu/uploads/sites/411/2014/12/PDF_Clopyralid_BeanDamage.pdf

Also see this re a contaminated garden - https://s3.wp.wsu.edu/uploads/sites/411/2014/12/Paper_Clopryalid_Garden.pdf

I'm wondering if what you're seeing is some kind of nitrogen burn, from poorly composted manure. Uncomposted manure is very powerful nitrogen fertilizer. Yes, lots of nitrogen will promote foliage growth, but too much nitrogen can cause stunting and leaf edge browning. I would expect this to happen quickly, however, as the stuff will leach out very efficiently.

Did you use the composted manure neat?

My test containers were 50/50 by volume compost and potting soil, mixed and fluffed together. Looking at the links provided makes me think it's probably more like unfinished compost because the tomato seedlings in the same containers are unaffected, unlike the beans that are showing odd growth. I e-mailed the company and asked some questions, and they replied that they have various tests they conduct on their compost just for this reason. Daninthedirt's comment is probably correct; the bags were very smelly and wet when first opened, but I just let them air out in storage for a week before using.

Keeping the stuff wet and well aerated will naturally decompose the urea, and outgas the ammonia. What you're left with is uncomposted organics with relatively little nitrogen. But if it started out being fresh manure, that urea is a heavy-hitter, nitrogen-wise.

I'm not sure what you thought you were going to "prove" with this "experiment", but using 50% manure, composted or not, as a potting mix is not going to
work well and it's not the fault of the manure. It is not meant to be a
potting soil, it's meant to be an amendment for garden soil in far less
than 50% proportions.

That seems a bit harsh, but that's the internet. I don't normally use composted manure, and it was simply a basic compost test to start seeds in it and see how they grow. I read some posts and watched some videos that suggested 50/50 in small containers, so that's why I used that ratio. I see weird leaf growth and wonder what causes it. I didn't think about nitrogen burn, and I didn't consider compost being unfinished, so I that's why I ask what happened. It's not proving anything, it's asking questions and hoping to learn from it.

lazy_gardens,

I suspect he was concerned about potential herbicide carryover in the manure.

See this info how to do a bioassay with potentially contaminated organic sources -- https://s3.wp.wsu.edu/uploads/sites/411/2014/12/PDF_Clopyralid_Bioassay.pdf

Fully composted manure isn't recommended as a potting mix ingredient but really, it's just organic stuff, and while the water retention and permeability may be a bit weird, you should be able to grow stuff in it. Nutrient-wise, it'll be fine. There is something else going on here, and the OP is right to be concerned.

It was a test! Please read the supplied links.

A germination test like this is often recommended. But I assumed it was a germination test only and that you didn't have to grow the plants for very long. Very possible the manure was not very well composted, and on top of the fact that manure isn't a very good potting mix texture-wise, maybe it's not to surprising. Jean's link above recommends germinating and growing for 14-21 days only.

It was not a germination test. It was a bio-assay --- a test to determine if certain pesticides were in the manure, composted or not. Some pass thru the animals intact, and persist in the manure unless actively hot composted for a year

Sorry, perhaps I used the wrong term. Quite familiar with the 'toxic compost' issue. I was only trying to point out that the OP grew the test plants for a pretty long time.