I purchased some Gardeners bagged composted steer manure at Lowes. I don't trust steer manure to be free of herbicides. I want to do a bioassay by starting some seeds. I don't know how much manure I should use in the test mix. 100% would be too much. Would 20% be enough to get a good test? I also bought Gardeners composted chicken manure. I am less worried about that stuff but I am also going to test it.

What % does the bag recommend and what % are you planning to use in your garden?

I don't know what the threshold would be, but I looked up your product at Lowes and next to "organic" there is a check mark.
The brand of steer manure sold at my local Lowes is Black Cow $5.99 cu ft and I use at least a trowel full in each planting hole. I'm suspicious of cheaper manure products which are mixed with "compost".

- Lisa

If you are using bean seeds to test for herbicides, it probably doesn't matter too much, as beans are very sensitive.

Bagged cattle manure is usually collected at feed lots and can be high in salts, but every product is different.

The bag recommends 1 part manure 4 parts soil. Ingredients listed are only composted steer manure. But in Lowes's specs listed they also indicate recycled forest products.

I am not concerned about how well it is composted or if they also use forest products. What I don't want is herbicides. I only will use a small percentage in various ways, both as a soil amendment and also a little in containers. Dealing with herbicides can take years to mitigate which is what I am worried about. I don't trust what they say they use which is why I want to test it for myself. There have been reports of herbicides found in OMRI listed products. The producers don't know if their product includes herbicides unless they test each batch. There is a good chance of herbicides with hay which is eaten by many animals and shows up in manure.

If I use too much manure then the seedlings may not do well from too much manure and not as an indication of herbicides.

I will be using bean seeds and tomato seeds for testing. My bean seeds are old so I may have a problem there. When I was researching bioassay the rec was to test with the crop you want to grow. There were also recs for different seeds for different herbicides. I mostly grow tomatoes so testing with tomatoes makes sense. I will also be growing squash and basil.

I have to worry about the chicken manure too.

Conventional agriculture practices include glyphosate-based herbicide (GBH) use.
•The risk of GBH residues ending up in poultry feed is high.
•The manure of poultry birds given such feed contains high residues of glyphosate.
•Crop plant growth and reproduction decreases if such manure is used as fertilizer.
•Glyphosate contamination in fertilizer may affect herbivore resistance of crop plants.

https://www.sciencedirect.com/science/a ... 9720349512

The ratio used for clopyralid/aminopyralid contamination is between 1:1 and 2:1. I have some peas in a 1:1 mix of horse manure and potting mix.

Careful with that chicken manure...high saline content.