I conducted an interesting experiment three years ago and called it my "living compost heap"
Turned out to be the most successful of my gardening experiments.
I have some raised beds which are about 3 foot square and 18 inches deep. I put posts in the corners of one of them and placed some metal netting around to almost double the potential depth.
I tipped in lots of bags of pretty well FRESH horse manure which I then covered with a shallow layer of topsoil and compost.
Year 1 - I planted two climbing courgettes in the bed. As time went on I continued to add various bits of compostable stuff to the surface whilst the courgettes were growing. The courgettes went crazy and, being trained up thick poles, I soon had what looked like a Brazilian rain forest
Year 2 - continued the experiment replacing courgettes with tomatoes. Never seen anything like it. I had "sweet millions" - For the first time in my life my produce looked as good as or even better than a seed packet photo
Year 3 - Runner beans
This year I have dismantled the experiment but following the success of year 1 - I no longer worry too much about rotting the manure down. I just chuck it on - except for area where I want to grow carrots, as explained by other posters.
This years experiment involves filling half a large pot with fairly fresh horse manure, topping up with soil/compost - and growing Maskotka bush tomatoes. Watch this space.
Good luck with the veg growing