I was wondering the same thing, and I guess we'll find out. I cleaned out the chicken coop last weekend, and put it all on my baby garlic plants. The shoots were maybe 4" tall. I had
enough used litter/poop mixture to go down about 3-4" thick. I already have a couple little shoots poking up through the litter/poop mix.
For reference, my litter consists of one 7.5 cubic foot bag of pine shavings, in a 4x4' coop with 11
chickens, where it initially sits 6+" deep. I stir it up at least weekly, and after 2 months when I change it, it's about 4" thick, with no wetness or bad odor, or any noticeable odor at all, really. I don't know if this is really considered deep litter, but it works well for us.
I suppose I'll find out on the spring if my little garlic plants come through, or if I messed up and killed them.