Don
I’ve tried using horse manure for a variety of things, laying it down as a mulch in late October for the following spring – I’ve never had anything but good results with a winter’s over-weathering.
Comfrey will actually grow beautifully the following spring even if you apply a mulch of ‘fresh’ horse manure. I wouldn’t really recommend that on the vegetable patch though.
Asparagus yields the past two years have gone up each year as an overwintered horse manure mulch has been applied.
Potato yields have been excellent.
This year I am extending it to where I will grow peas.
The worms absolutely love it and the numbers of worms in my garden now is far higher after two summers of a combination of no-dig and over-wintering manure/compost/mulch/winter crops.
Fruit trees have benefitted from