Used some on a trial bed by the house along with the spent tomato pot compost (huge organic content of root system) and planted shallots in it. They did very well once the cold March was over.
I put some more down on a few more beds a couple of weeks ago, including one with winter onions and garlic. I’ve done no scientific measurements, but all the young plants shot ahead in the week after putting the dust on top.
I’ve also just laid down some horse manure on top of rock dust on ground not dug since last spring. We’ll see how it gets on. Same on top of the asparagus and rhubarb.
I also put a small handful into the final pots of my tomatoes last summer, which was a mixture of John Innes Number Three and purchased well-rotted ‘farmyard manure’. No science done, but the final outcome was magnificent. I suspect lots of hot summer sunshine helped too though.