Google says - Asparagus IS sensitive to juglone (the toxin the black walnut roots give off). I wonder if you move them to another spot if they would recover. I hope so.
I can't say for sure, because I haven't tried planting asparagus around our black walnut trees, but I don't think they're going to do well if you leave them there.
Sorry - it sounds like you put in a lot of work to prepare the bed so I'm sure it must be frustrating. There are many lists of plants on the internet that WILL tolerate juglone if you decide to put something else there.

Here is a link that might be useful: Google search for

I have planted a few asparagus crowns this year as I do most years. Not all of mine came up either. Sometimes I plant them then forget them in our dry summers. They can be slow to come up and take off. When I get mine they are in bundles dry with a rubber band around them. It doesn't surprise me that it is a stuggle for them to sprout roots and put up foliage. Drainage could also be your problem if you have heavy clay. I use wood chips on top as a mulch if I use them. I don't think it is good to mix wood in to the soil. Pine bark and bark fines are used sometimes as potting mix and to lighten soil, but I don't think wood is good. I doubt that is the problem though. I have walnut trees in my yard and around it. When something doesn't thrive or dies, I never know if it is the walnuts or not. I know hostas and daylilies will grow under them. But I always try to plant potatoes and tomatoes far away because they are supposed to be sensitive. I keep trying with asparagus. I have shallow rocky soil and really good drainage. Our hot summers challenge me to keep everything watered. I have some asparagus but I want more and keep trying.

I checked online this morning and found several sites that list asparagus as being sensitive to the juglone from black walnut trees. I also looked to see if I could find any way to neutralize the effects, but didn't see much other than about composting leaves. I'm going to dig up my asparagus bed and move everything.

But does anyone know if there is a way to neutralize the juglone in the soil?

I don't know of anything you can add to neutralize the juglone. Clay soil tends to hold the juglone in a higher concentration. I've read that the juglone stays in the soil for a long time after trees are cut down.
A raised bed with good drainage would help for plants that aren't deep rooted but I think asparagus does have deep roots doesn't it?
Don't plant tomatoes close to black walnuts either. They're very sensitive.
If you're looking for an edible to plant there, Black Raspberries are supposed to do well.

What a sad story for you. I hate when those kind of hard-work-with-no-luck results happen. Let us know if you were able to salvage them. I'm not sure the roots will still be transferrable, but hey. What do I know? I've never had black walnuts. Good luck!

I was going to answer that I put asparagus in pots sometimes because when I buy them I'm not always ready to plant them. Then I thought of how much money I spent on potting mix this spring. I use very big pots or half whiskey barrels otherwise you have to water often. You can put a petunia or something in with them and they don't look bad. When they are big strong plants and the weather is cloudy and rainy you can slip them in somewhere. Once they are established they keep coming up and can be neglected although it is better for yield to take good care of them.