Here’s what I’ve seen:
1. Asparagus coming through in leaps and bounds right now – 45 spears visible on a 5m * 1m row of crowns and we’ve already eaten 4 spears last week. As good if not better than last year.
2. Huge increase in the worm population and worm size both on main beds and fence-side beds. Up to 15cm in length and 1cm wide.
3. 100% take rate of garlics in March. Winter onions and autumn garlic have grown on tremendously with a top dressing of horse manure put on when the rains got ridiculous(around January)!
4. Autumn raspberries planted last summer have tremendous foliage this April (here the manure was put down in March after rotting for 4 months).
5. Brilliant flowering of pear, plum and cherry trees (no doubt due to the mild spring too).
6. Phacaelia germinating very rapidly after spreading on a hedge-side bed covered last autumn with horse manure.
7. Comfrey and rhubarb have roared away this spring: already cut comfrey leaves for the early April potato plantings and we’ve already had 5 pickings of rhubarb.
The verdict on the potato beds I still await.
So, overall, you won’t harm your beds using horse manure as a top dressing and you’ll improve the worm population enormously.