I am gotten to where I do not add unknowns. I just don't do it.I use a few different composts, but I really like Horn Of Plenty on Etsy. It doesn’t contain any manure & there isn’t a lab report. Those things may be a nonstarter for some, but it’s truly some beautiful & clean stuff.
I started actively making compost from the early 90s. Somethings back then were easier and some were quite more difficult compared today. There were quite a few inputs that you really did not have to worry about, but you do today. I would be extremely cautious of dairy manure today. Naturally, I always had known the dairy operator and knew how he ran his operation. The likelihood of me finding the same kind of operation I utilized back then, is pretty slim. Unless they are a specialized dairy. And if I was them I would be marketing my manure!
I've had analysis run on large Input items that I was either going to utilize or that I had purchased. and the purchase was always stipulated that it would be based on analysis as the final closure.
A fine example was that was a quite sizable purchase of cotton seed meal. This was from semi-organic*** farms in the Panhandle that did not utilize a spray to kill the cotton in order to let the bowls open up when it died. Natural early frost did the same job. It came back extremely clean ! I've looked, they don't even offer the same product anymore.
And I have to be pretty cautious on my inputs since I reuse my media. Along with cannabis being a concentrator, I'm just not gonna take the chance without the documentation.
And that's pretty much why I'm a BAS fan. Jeremy is Loyal to the soil and just a plain fanatic About clean analysis and sustainability sourcing. That's exactly how I would do it if I were in his shoes.
***Semi-organic................ They may have used organic fertilizers or salt fertilizers, but no inorganic pesticides or any arsenic sprays to kill the plant in order to harvest.