Try this excerpt from my Course Book
"As with compost itself, the important factor of its cost varies so much that value for money is hard to assign. I suggest that £20 per tonne delivered is reasonable. Year old animal manure is more valuable than woody green waste compost. One tonne is enough for spreading about 2-3cm (1”) of compost or manure on 60-80m length, of beds 1.2m wide (4×100-165’, about half an allotment).
For a first season of thick mulching (7-10cm or 3-4”), to improve soil and reduce weed growth, a three or four ton load could be spread on new allotment beds. Thereafter one or two tonnes per annum is enough to keep improving the soil."
ALLOTMENT SIZE (of standard 10 rods) is one sixteenth of an acre, about 300 square yards, say 150 yards length of four foot wide beds and two foot wide paths. Adding these together makes six feet or two yards, and 2×150 = 300).
Weight per square metre of beds, allowing that beds are two thirds of the total area (paths are one third) and counting metres as yards, roughly (!), is approx 40kg for 3-4 inch thickness and 20kg for annual maintenance dose of 1-2 inches. Please allow for different densities of manure, this is to give a rough idea.