[Chicken Pete]

I am sure this question has been asked before but I cannot find it..
What is the best manure for the allotment, we are able to get well rotted pig manure, lots of bags of horse manure and cow manure from the local farm.  Are there special crops that grow better in different manures or are all manures good for the soil?
Also, If you spread a good amount over the allotment how long (in years) before the ground needs more manure dug in?
Thanks in advance for your advice.

[Trillium]

Here you go:

http://www.allotment-garden.org/fertilizer/farmyard-animal-manures.php

How often to add it depends on what you're growing, and if you're working your ground in rotation. Potatoes will always need manuring but crops following in the same spot will need no extra manure.

Then there's the existing soil condition to consider. If the soil is in poor heart, you'll just need to add for a few years and then taper off. Check around the above link for more info on how often to add manures as there are more articles.

And do be sure it's rotted manure you add in spring, never fresh (which is good only for winter application or composting)

[mumofstig]

If think if you manure the potato area each year, it is a manageable system.

This explains it better than I can  
http://www.allotment-garden.org/vegetable/crop-rotation/three-part-crop-rotation.php